Fiber Reinforced Gypsum
Akilli
Can ordinary non-AR glass fibers be used to reinforce gypsum?
Much Obliged,
Ethan Gross
sculpt...@my-deja.com
in reinforcing plaster.
I still prefer the use of Sisal, or rough hemp because this material
can be layed up in volume far faster than glass- is far cheaper ( a
bale of sisal will make about 100 medium sized palster molds at a
cost of about 170 USD)
Also- the malleable mass of sisal, saturated with a thickening
plaster can actually be Sculpted and modeled into a wide variety of
self supporting forms ; as the plaster thickens you can form feet,
reinforcing flanges, separation planes, and in every way control the
final form and thickness of the casing part.
I recommend everybody who uses woven maerial or glas mat
should try raw sisal for a few molds- theres no cutting, no
puckering and no difficulty getting the reinforcing to folow the odd
contours of the molds surface.
Christopher
Sent via Deja.com
http://www.deja.com/
Michael Gainer
polyurethane foam from a spray can (home insulation crack filler)
to make mother molds because:
- it's light
- it's strong - not brittile
- it's very easily carved to give a flat surface
- it's flexible enough to let you cheat undercuts a little bit.
Having seen a bit of the discussion here about the health risks
associated with isocyanates, I'm planning on going to rigid mother
molds. I had been planning to use FGR-95 and chopped strand glass
as a mother mold. Not having done it, I see the primary advantages
as being:
- thin,
- light (compared to other rigid options)
- strong - not brittile (compared to other rigid options)
Could you please comment on the relative thicknesses of glass-
reinforced versus sisal-reinforced gypsum required to get enough
strength for, say, a torso or slightly larger-sized piece?
I'd rather spend a bit more on materials if it'll save wear and tear
on my back, but if it's pretty close.... Also, what flavor of plaster
is appropriate for sisal - #1 moulding, FGR, <mumble>-cal,
<mumble>-stone? Secondarily, what volume is a bale of sisal,
and can I reasonably expect to find it in smaller quantity?
sculpt...@my-deja.com wrote:
--
Mike Gainer
http://www.bnglifecasting.com
Gary Waller
The hemp is a great choice, and God knows those marijuana farmers need all
the help they can get. When I worked in an Italian shop they called it
"stowpa" (as it sounds, not as it is probably spelled). The fibres are
fluffed up into bundles. The great advantage over glass is that the "hairs"
which can often stick through a casting are easily burned off with a propane
torch. Glass "hairs" are a real pain. The disadvantage is that they retain
water a lot longer than glass, and unlike glassfibre Forton, can never go
outside (or cool, potentially moist mold storage area). Vast areas of
ornamental plaster have been made over the years using "fibrous plaster" -
woven burlap reinforced plaster. In general "fibrous" plaster is lighter
than casting with hemp strands - thats why it became so popular in the late
1800's and early 1900's.
The advantage of glass fibre mats is their unbeatable strength to weight
ratio. A super strong Forton composite about 3/8" thick will weigh less than
2 lbs a sq ft. The "AR" glass is for concrete only, the "E" glass is the
common one used for everything else. Most often the shops use "chop glass"
mixed right into the plaster backing coat. Chop glass is cut fibreglass
roving (threads), I run mine through my Glascraft chop gun but you can buy
precut, the smallest for small sections is 1/2" or you can get up to 2" for
large flat sections.
I still prefer polyester or epoxy resin reinforced tooling (no rubber) for
any type of money making venture, but thats a road already travelled.
ubg...@my-deja.com
working characteristics and performance stats than regular plaster
(with sisal or without) or even regular hydrocal. It can be cast quite
thinly when used with fiberglass matting. The following procedure was
recommended to me by a tech at USG and has worked very well for large
castings at a thickness of 1/4 inch. It will be extremely strong and
relatively light, though the hydrocal is heavier per setup volume than
regular plasters (its 3Xs as dense). The weight reduction is achieved
by keeping the casting thin.:
Mix slurry in proportion of 100pts dry FGR to 30 pts water by weight.
Measure carefully and consistently from batch to batch. The FGR must
be mixed at that proportion. It will seem too thick until you mix
thoroughly--don't worry about sifting it in as with regular plasters.
It sets slowly so you have plenty of working time. Lay up a surface
coat on the inside of your mold. Then cut your fiberglass into
squares, dip them in the slurry and back up your surface coat. You may
want to let the surface coat set up slightly before applying the
fiberglass but be sure to get at least one layer on in the first
batch. It bends relatively well around the form but watch out for
trapped air pockets since the matting can be slightly "springy" until
the slurry gets thick. I use three layers of matting. Really you
don't need it any thicker than 1/4 inch--it will fool you. A slightly
over life-size torso done like this will be light enough to be easily
moved by one person. I fooled around with chopped strand as an
alternative and rejected it in favor of the matting, but that was so
many years ago I can't supply any details.
In my experience, the hydrocal will accept up to 50 grams or so of
oxide pigments per pound of dry FGR without any appreciable loss of
strenth, but you need to add a tad more water to keep the slurry from
being too thick due to the additional powdered element.
I don't believe it would be wise to use sisal in FGR since it is
formulated for glass fiber. However, sisal and standard plaster is the
age old method for both castings and molds. Look inside an old plaster
cast in a museum and you will see it.
In article <3A77379F...@svnetworks.com>,
Michael Gainer
> FGR 95 [... detailed instructions on how to use FGR-95 with fibreglass mat
> ...]
Thanks for that thorough treatment. It's really nice not to have
to do the experimentation on my own. Some more questions
remain though, if you please...
- What weight of glass mat do you use, and does it really matter -
does a heavier weight give me more strength, or just more co$t?
- Is that mat, or woven (apparently, the oz is per square foot for
mat, and per sq. yard for woven, at least per Douglas & Sturgess'
web site, so I think I need to know, in order to sanely order stuff.
Hmm. I just did some math. Let's say we want a 1 sq. yard panel,
1/4 inch thick. That's 3 ft. x 3 ft x 1/48 ft, or 0.1875 cu. ft. USG
says FGR 95 is 112 lb/cu ft, so 112 x 0.1875 = 21.00 lb.
USG wants 5% of that weight as glass, so that's 1.05 lb.
Now, I dunno from glass mat, but what I can get locally by the
yard (rather than the whole roll) is 1.5 oz mat from Douglas &
Sturgess. At 1.5 oz / sq ft, that's 13.5 oz per yard, and if we
want three layers, then it's 40.5 oz, or 2.5 lb.
So, lemme see... 3 yards, at $2.50 per yard is $7.50, but 1 lb
(all USG sez we need) of chopped strand is only $2.50.
(mind you, all this in over-the-counter quantities, not pallet
loads (nevertheless, I expect both get cheaper at about
the same rate in bulk))
My intuition says that one layer of mat isn't going to really
do a heck of a lot to the tensile strength of the gypsum, so I
really do believe in that 3 layers as necessary. So, last question:
Does 2.5lb of glass (mat) give you 2.5x the benefit of 1 lb of
glass (chopped fiber), and is it such a noticeable benefit that
I should go for the 3x cost?
Or should I shut up with the annoying questions and go do
some strength testing on various materials like I've been
meaning to for several months now? Or go pester USG?
Andrew Werby
than fiberglass in any form. It's not actually hemp, by the way, (although
it's often called that) so don't bother smoking any. Sisal fiber is derived
from a plant a lot like the agave, used for making tequila. It replaced hemp
in the US for use in rope when policies shifted from the encouragement to
the discouragement of cannabis cultivation.
I also use the fiberglass scrim cloth sold by Douglas and Sturgess, and it
is handy for applications where thinness and flatness combine. It has to be
cut to shape, but its open structure lets it accept the plaster without
making air pockets. Three layers make a fairly strong mold in about a
half-inch of plaster. Even if it breaks, the cloth will hold the pieces of
the mold together.
I haven't used chopped strand since college, where they were big on the
stuff- I still itch whenever I think about it. Some people swear by it- I
only swore at it...]
Andrew Werby
http://unitedartworks.com
Michael Gainer wrote in message <3A7789FC...@svnetworks.com>...
sculpt...@my-deja.com
producing a hollow, lightweight casting out of gypsum- although
the chop gun is much easier and in my mind generates better
results for this application. (alas- I do not have a chop gun)
However- because of the features that a mold casing must have to
be truely srong and useful I still use sisal for all casing work. While
glass has a stronger tensile srength per cross sectional unit- it is
precisely the lack of cross sectional area that makes it weaker
than sisal.
For half the unit cost as an eighth inch thich glass coat you can
have a 3/4 inch thick sisal coat- this third dimension makes for a
very strong casing.
Christopher
sculpt...@my-deja.com
it.
Sisal is also called casting fiber by some suppliers- it is
remarkably strong and Andrew is right- though often called hemp,
it ain't cannabis- The stuff I get is made of the same material as
Manila Rope.
A bale is about 3.5 feet by 2 feet square but can also be bought in
a "flake" which is about a quarter bale.
As I mentioned to Gary, I often will use a glass matt called veil
cloth to make cast figures out of- the random and loose nature of
the mat allows it to follow contuors more closely than a regular
weave- but glass is still expensive and at best difficult to work
compared to sisal.
if you are new to these techniques I would start with sisal since it
is far more forgiving and check out the plaster working FAQ I wrote
for Andrew's website.
As to plaster- there is no better grade of plaster than Puritan
Pottery Plaster- but this USG product may not be available near
you- call the manufacturer available to you and ask for a plaster
with no fillers or surface hardening agents and a long plastic
stage. Or ask for something comparable to Puritan- if they make
plaster they should be familiar with it.
christopher
Dan Spector
certainly cheapest, but if light weight is important, ya gotta go with
glass. FGR 95 is almost indestructible, but hard to buy. Hydrocal/glass is
very, very strong. I am able to make thin flanges which I drill thru and
bolt my support molds together, or for just a few uses, screw it together
with drywall screws.
In answer to the mathematical analysis, if you're using FGR95, you're
loading it with all the mat you can get in there. I don't know about your
weight ratios.
You can use 1.5-oz. mat on flat and simple curved surfaces, but the thinner
mats do better on complex articulation. Their sizing dissolves quickly and
they can be pushed around easier.
Keep in mind that the face layer of a support mold can be cheap #1 casting,
and then when you have a smoothed-out surface, come back with the Hcal
lamination.
Alternatively, a support mold needs no great surface. Laminate directly and
the voids and porosity will never bother you.
If you will be direct-sculpting, stick with sisal, never use power tools on
a glass lam or the air will be full of itchy silicosis.
--
Dan
<archica...@earthlink.net>
http://www.archicast.com
----------
Gary Waller
production mold. I start with clay or lime modelling putty, for rough
sketching, freeze that thought in plaster, recast in plaster using a waste
mold and then carve the plaster casting. If it is to be more finely
detailed, I build a plaster piece mold, cast in resin, and then detail and
polish the resin with power carving tools (dremel, etc.). If I am happy with
the piece, then I make a piece mold in fiberglass resin - gel coat (or
epoxy), veil and then roving. If it is a really big piece mold, I will add
galvanised steel channel stiffeners and/or make a "sandwich" with
polyurethane foam or balsa between the face coat and the backing coat. An
jigs or cradles for routing or clamping are also added at this stage. This
is for production work - scenic work is a whole different category as are
limited edition works of art.
By using fiberglass and resin as piece molds you gain superior strength to
weight ratios and I am very pleased with the cost, even using premium zero
shrink, tooling resins such as Reichold prolite vinyl ester. I can cast up
to 300 degrees, the surface is super durable, there is no shrinkage,
expansion or warpage, and the molds can easily be modified or repaired.
Special ventilation is required, special equipment is required, but these
are a relatively small price if you factor in all the other costs of doing
business - ie making more than 100 of any one item. While these molds are
fully capable of casting plaster, there is no money in casting plaster - it
doesn't ship well, it doesn't retail well, it is expensive to finish.
Polyresin can be made to look like any material - including antique
plaster - ships well, retails well, is easy to finish and it can go outside.
The acrylic modified plasters were/are an attempt to capture that lost
market, but these materials are nowhere near as durable or inexpensive as
polyester. The metals are still the king of the art casting market and this
will always be so.
Lime plaster/concrete is a brilliant surface for painting fresco, scratching
a sgraffito, making delicate hand modelled ornaments, or making a classic,
beautiful wall or ceiling. For this reason its use will never die. The
modern gypsums have, by in large, offered very little to the world of
aesthetics - they quite rightly have been associated with the Victorian era
of overly fussy, weakly cast, interior ornament. Their use, or rather abuse,
has brought down the plaster trade and its old skills to its knees. There is
currently a tremendous interest in reviving these old skills, but the key is
realise the strength and weakness of every material or technique - the
public demands results, not a history lesson. The public demands things
which "taste good", not things which are "good taste".
sculpt...@my-deja.com
Plaster is not suitable for finished product- It is a tooling material-
when I make rigid mold out of it I am principally interested in the
ease with which I can tool and sand and finsh the Interior of the
mold surface- so that I can generate a much better surfaced
casting- often in resin.
Plaster is also not suitable for production rigid mold systems.
(other than slipware and latexware that rely on the absorbancy of
the plaster to create the casting)
For production rigid molds I generally rely on resin- or vacuum
formed materials, or spray-metal molds.
While plaster is a wonderful material for tooling and generating
molds and masters rapidly and inexpensively- and makes an ideal
casing for an artist's rubber molds- it is too fragile to be effective in
a high production- low skilled labor environment.
While I will use plaster to design and create masters for
production mold systems- I usually end up with a mold that will
cast production rubber mold casings in urethane- which is
relatively unbreakable and quick to cast- allowing me to put
dozens or hundreds of identical mold casings on line within just a
few days.
Or- in china, where labor is cheaper than water- I have them
laminate glass casing parts for their durability and light weight.
However- i maintain that plaster- as a low cost, highly versatile,
easily stored and essentially non-toxic material is still the most
useful all around mold and master making material for the fine
artist. it is more forgiving and easier to work and, once mastered,
can be easily adapted to far more uses than any other single
material.
Andrew Werby
[I'd like to rush to the defense of my beloved Modified Gypsum plasters, if
I may. First of all, it isn't fair to blame these excellent materials for
the demise of the the plasterer's trade. This has been brought about by
changes in building practices and aesthetics, not by any shortcomings in the
materials. In fact, glass-reinforced plaster is the only kind used in
buildings any more, when ornamental details that are strong, light-weight
and fire resistant are called for. If it wasn't for this stuff, there would
be no jobs at all for plaster-workers, period.
While I certainly won't dispute that bronze castings are stronger than
plaster, however modified, I feel that gypsum, as a final material, has a
place that is unique and valuable. Part of the reason has to do with its
properties; it is much less toxic than any resin system, so an individual
artist can use it in the studio without shortening their lifespan. The new
polymer-added systems are much harder and less fragile (at least as strong
as low-fired ceramics) and are easily painted or even patinated, if powdered
metal is added to the mix. While it doesn't fare very well outdoors, most
sculpture is kept inside anyway. When you consider all the materials used to
make sculpture these days- from wax and feathers to fish and formaldehyde-
I don't see how a material as versatile as plaster can be denied a place at
the table. Of course it has been abused in the past, but the Victorians did
fussy things with bronze too- you can't blame the material for what's done
with it. But when I see the horrible resin castings coming out of the Orient
these days (they seem to delight in copying the worst excesses of cast
porcelain and adding garish touches- think of shepherdesses made-over by
Revlon) I realize it's hard to resist.
As for the economic argument; that plaster-based artworks are hard to sell;
it's true that they won't command the price of an equivalent-sized bronze
casting, but on the other hand, they are much cheaper to produce. For an
individual artist, it's usually difficult or impossible to finance an
edition of bronzes, and it's easy to make a lot more molds than one has any
chance of casting in the "king" of materials. It is certainly much more
feasible to cast an edition in a hard plaster, and to sell them for a
fraction of the price of bronzes. Even if one is set up to cast bronze
oneself, that's a whole lot of time and effort spent on the process that
could be spent on the creative side. I don't understand the claim that resin
is cheaper (even if you leave out the hospital bills)- volume for volume it
always has been much more expensive where I've shopped. For example, Douglas
and Sturgess sells their basic polyester for $109 per 5-gal. unit; but 50
lbs of Tufstone (a polymer modified fiber-reinforced gypsum cement) which
makes more than 5 gallons of material, costs $17.00.
Of course there are public perceptions to overcome; people are used to cheap
plaster-of-Paris castings that are soft and easily damaged, but the newer
formulations are much tougher- perhaps some education is in order. I doubt
you'll find one that actually "tastes good" (chocolate castings do, if
that's what's called for) but at least plaster doesn't smell bad, like
freshly cast polyester. I agree, though, that what's needed is an educated
appreciation of the strengths and weaknesses of our various materials, in
order to come up with the right one for a given situation. Frankly, I think
the "public" in general doesn't have a clue...]
Andrew Werby
http://unitedartworks.com
Michael Gainer
> which
> makes more than 5 gallons of material, costs $17.00.
50 lb * 2.2 lb/kg => 22.72 kg .
Recommended consistency is 32; 22.72 * 1.32 = 30.0 kg.
Mixed density is 2.0; 30.0 kg * 1 liter/2kg = 15 liters = 16 quarts = 4 gal.
Four gallons, to within a couple of percent. I don't know a lot, but I
do have some experience with Tufstone. Is there a prize for the smallest
nit picked? Other than the usual rewards of being this anal?
Andrew Werby
Michael Gainer wrote in message <3A7EF100...@svnetworks.com>...
(if you're limber). But thanks for the correction, although I don't think it
changes the basic point I was making, in response to Gary's statement that
MG was more expensive. I haven't used Tuffstone much- what do you think of
it as a final material?]
Andrew Werby
http://unitedartworks.com
Gary Waller
Andrew Werby
http://unitedartworks.com
A fifty lb sack of plaster/MG/tuffstuff would fill about one half cubic
foot (about the same volume as the powder in the bag). An important point is
that while I see that many sculptors solid cast MG - it is not designed for
this purpose, a smooth surfaces develops 'micro-crazing"- a network of small
cracks which does not effect the strength, but does effect the appearance.
The remedy is to make sure that the fiberglass reinforcement is closer to
the surface. Another problem in solid casting MG is that it should have more
defoamer added otherwise you will have problems with air pockets, etc. I
have experienced both these problems.
You are paying about double what I would pay for polyester resin. If cast as
"polymer concrete" you would add up to four parts sand, walnut shells,
microspheres, calcium carbonate - each has their advantages. For garden
castings, or "bonded marble", as seen at websites like
www.henandfeathers.com they are probably lees than 20% resin., with a higher
percentage (or gelcoat) in the face mix. One gallon of resin ($5) can be
diluted with fillers to make up to 4 gallons of volume. - if this is sand,
it would be as heavy as normal concrete however. The casters wash the
castings in warm soapy water, leave overnight, to get rid of the smell.
What has happened to the ornamental plaster trade would be the equivalent of
"wallpaper" completely supplanting the decorative painters trade. Decorators
would get so used to using the paper, they forget what is what like to
custom paint a room, and soon those skills are lost. Over time the
wallpaper, being a manufactured product (like generic ornamental plaster),
would soon become marginalised because there are so many inappropriate
installations and stylings.
Lets hope that some new casting materials show up on the market. Has anyone
tried solid casting Aqua Resin - wasn't Battersby playing around with that?
Gary
Michael Gainer
Andrew Werby wrote:
No, I agree wholeheartedly with your point. As an inveterate geek, though I
just had to.
Tufstone is very very nice, so long as you completely disregard any advice
you ever heard regarding how to mix plaster. At the consistency of 32 that
USG recommends, sifting it in, however slowly, leaves you with about 1/3
dry plaster that just won't sink in. I usually mix a 6 liter batch at a time,
by dumping plaster into water, and mechanical mixing for 90 sec, and then
vacuum it. With very cold tap water (pretty pure - no accellerators or
retardants) it has a nice long fluid phase - plenty long enough to get a mold
wetted out, and do something else for a couple of minutes. Once it starts
to set, it allows enough time to do hand layup into a roughly 3 sq. ft. area,
but not so much time as to be tedious. Accellerator or hot water is an
invitation to a solid plug in your mixing/vacuum container for large batches.
Once set, it demolds nicely, but is fragile at sub-millimeter detail until the
surface is thoroughly dry - a day or so, in semi-arid (Northern California)
kind of humidity. Once thoroughly dry, it takes power tools or a lot of
patience to trim to size, but surface hardness keeps minor handling errors
small.
It is not terribly forgiving of chiseling; it loves to fracture at a well
defined
crease, but it will stand a pretty fair bit of nibbling before it does so.
Re-mixing and patching holes is somewhat problematic - mixing with very
little water gives a comparatively very dark product, which really stands out
against the rest of the piece. 1-3 mm scale blobs can be carved off with
dental sized tools. Larger issues need to be pre-wetted to soften them before
attacking.
Andrew Werby
Battersby wrote in message <_D0g6.1371$I45.1...@typhoon.austin.rr.com>...
>> Andrew Werby wrote:> > I haven't used Tuffstone much-
>
>What is your preference when it comes to plaster casting Andrew??
[I've mostly used Forton MG for final-product casting. I like its
flexibility, in that a wide variety of fillers, fibers, pigments, and
powders can be added if desired, as well as its toughness and impermeability
once fully cured. I'm not in love with the stuff, though- drawbacks include
a long period of weakness in the mold (wait 2 days before unmolding anything
delicate), the complexity of weighing and mixing all those ingredients, its
tendency to adhere permanently to clothing, moldshells, and anything else it
touches, and the way the dry melamine resin wants to turn into a useless goo
from absorbing moisture out of the air. On the other hand, the tests I've
had out in the California weather (not "real" weather, I know) have shown it
to be remarkably durable outdoors, at least absent a lot of freeze/thaw.]
>
>Michael Gainer wrote> Tufstone is very very nice,
>
>I agree with you on this Michael. This is a great product. Really
convenient
>that it comes in the bag already fibered, or unfibered. It pigments nicely,
>and I have found that it is extremely resistant to chipping.
[I didn't realize it came unfibered. Does D&S carry it that way now, or is
it a special order item? I agree, the convenience of a single-component
product has a lot to recommend it.]
Andrew Werby
http://unitedartworks.com
>
Battersby
> > You vacuum your plaster?? Why?? Would you mind describing the process??
>
> Sure. I have a section of 6 inch PVC pipe capped with 1/2 inch of
> acrylic, about 18" long. This is pretty much governed by the length
> of the shaft on the drill mixer. I have a vacuum pump attached to a
> hose which runs to a flat plate, which goes over the end of the pipe.
> The vacuum pump is to get rid of the bubbles introduced by
> overzealous mixing.> to do hand layup into a roughly 3 sq. ft. area,
How often do you change the oil in your pump Michael?? Seems like you would
be shortening the life of a significant investment. I'm pretty ignorant
about mixing h2o and vac pumps.
> > Why do you prefer TS over TufCal, which is designed for thin wall work??
Or
> > am I misunderstanding you??
>
> Douglas & Sturgess don't carry it. Like I said, my experience with
> plaster is very narrow, and mildly deep.
If you are happy with the results is all that counts.
> > Another question - I'm curious as to why you go back and forth from
metric
> > to the U.S. Standard feet and inches.
>
> Well, because it's so d@mn much easier to do the work in your head
Well I'm more confused now. I guess what you're saying is - if you are
familiar with both, then metric is easier. I was just wondering why in one
paragraph you would use liters to describe the volume, and then sq ft to
describe the area. How do you say 3 sq ft in metric?? Do you know of a good
metric tutorial on the web, or a good reference book??
Battersby.
> in metric. If you want to change scale, you just move the decimal.
> If you have the number for density in g/cm^3, then that's the same number
> as for kilos per liter. If you have density as USG provides it, in
lb/ft^3,
> what is that in oz/gal? cwt/bbl?
>
> I use English units because US suppliers provde stuff denominated in
> not-power-of-ten units like pounds, yards, gallons, oz/sq ft, and
> bizarrisms like wire gage, sheet metal gage, drill gage, and (less
frequently
> nowadays) plain numbers (i.e., "take a No.5 washtub filled half full,
and...").
> If you find you need 20 kilos of X, and X comes in 10-pound bags,
> you need to know to order three bags, not two.
>
> Plus, some folks have a better working knowledge of English units and so
> can give better advice or catch your mistakes. F'rinstance, suppose
> I ask for a 122 cm tall life-sized statue that can withstand sustained
> temperatures of 30C. So what? Change it to 48" tall .... 86F.
> --
> Mike Gainer
> http://www.bnglifecasting.com
--
T. M. Battersby, stuccoist.
http://www.battersbyornamental.com
tbatt...@satx.rr.com
Battersby
> I haven't used Tuffstone much-
> Battersby wrote
> >What is your preference when it comes to plaster casting Andrew??
>
> [I've mostly used Forton MG for final-product casting. I like its
> flexibility, in that a wide variety of fillers, fibers, pigments, and
> powders can be added if desired, as well as its toughness and
impermeability
> once fully cured. I'm not in love with the stuff, though- drawbacks
include
> a long period of weakness in the mold (wait 2 days before unmolding
anything
> delicate), the complexity of weighing and mixing all those ingredients,
its
> tendency to adhere permanently to clothing, moldshells, and anything else
it
> touches, and the way the dry melamine resin wants to turn into a useless
goo
> from absorbing moisture out of the air.
The equivalant product here in Texas is duoMatrix-G (gypsum + latex + resin
+ hardener). There is also duoMatrix-C. I don't like it for about the same
reasons you state.
> On the other hand, the tests I've
> had out in the California weather (not "real" weather, I know) have shown
it
> to be remarkably durable outdoors, at least absent a lot of freeze/thaw.]
Are these tests - raw, or sealed, or both??
Is AquaCast available out west yet??
> >Michael Gainer wrote
> Tufstone is very very nice,
> >I agree with you on this Michael. This is a great product. Really
> convenient
> >that it comes in the bag already fibered, or unfibered. It pigments
nicely,
> >and I have found that it is extremely resistant to chipping.
>
> [I didn't realize it came unfibered. Does D&S carry it that way now, or is
> it a special order item? I agree, the convenience of a single-component
> product has a lot to recommend it.]
> Andrew Werby
> http://unitedartworks.com
Why would you want unfibered TufStone Andrew??
Battersby.
Michael Gainer
> How often do you change the oil in your pump Michael?? Seems like you would
> be shortening the life of a significant investment. I'm pretty ignorant
> about mixing h2o and vac pumps.
About monthly. It seems to have lost some efficiency over two years,
but not crucially so. If it keeps up, it'll need a $500 overhaul next year.
At $15/month, that's pretty reasonable. As far as introducing water goes,
the salesman said to avoid phenolic vanes - they absorb water, swell
and bind. You now know everything about 'em that I do :->
> Well I'm more confused now. I guess what you're saying is - if you are
> familiar with both, then metric is easier. I was just wondering why in one
> paragraph you would use liters to describe the volume, and then sq ft to
> describe the area. How do you say 3 sq ft in metric?? Do you know of a good
> metric tutorial on the web, or a good reference book??
Hm. Partly, I'm a science bigot. Sometimes, it's definitively better.
Say I need 5 liters of volume. The density of silicone is 1.1 grams / cubic
centimeter.
5 liter * 1000 cubic centimeter / liter * 1.1 gram / cubic centimeter * 1
kilogram / 1000 grams = 5.5 kg.
Now, as soon as you do this about twice, you can skip over the
multiply-by-1000 and divide-by-1000 step, and just go to 5 liter * 1.1 = 5.5 kg.
In English, you need 5 quarts. OK, so, WTF is the conversion between
quarts and cubic feet? I don't even *know*. Figure that out, and then
multiply by 1728. Why 1728? Well, that's 12 * 12 * 12, and if your
supplier quotes in pounds per cubic inch, that's what you gotta do to
convert cubic feet to cubic inches. You're stuck remembering all these
one-of-a-kind conversion factors, or working them out every time.
Boring ranting aside, however cool metric is, I still gotta order
the silicone in 9-lb kits - except what I get *shipped* is a one gallon
bucket plus a one-pint bottle. Isn't it grand?
3 ft^2 is roughly 0.28m^2. If you have a Unix machine, 'units' is the
program for you. You tell it how much of what unit, and what units
you want it in, and it does the rest.
A reasonable start on the metric system:
http://edie.cprost.sfu.ca/~rhlogan/metric.html
Slightly geekier:
http://lamar.ColoState.edu/~hillger/brownridge.html
Links to everything you never wanted to know:
http://lamar.ColoState.edu/~hillger/
--
Michael Gainer
http://www.bnglifecasting.com
Gary Waller
Hey Tom, how does aquacast compare to the tuffstone.
Gary
Battersby
> Hey Tom, how does aquacast compare to the tuffstone.
As far as I'm concerned, AquaCast and TufStone are completely different
animules.
Dump the AC in your 16% h2o and mix. Place it in the mold and it just lays
there for about 20-25 minutes. Then it snaps set in about a 60 second
window.
After about the first 45 minutes you need carborundum or diamonds to tool
it. The expansion is only .002%. Promoted by USG as being waterPROOF. I
believe it, it's really dense. Takes pigment really nice.
Like MG said with the TS you can work with it for 5-10 minutes as it
stiffens up. The AC just lays there like a puddle, then it snaps quick into
a rock. Gets so hard a cat cain't scratch it. TS gets real hard too.
Battersby.
Andrew Werby
Battersby wrote in message ...
>Andrew Werby wrote
>> I haven't used Tuffstone much- [I mostly use Forton MG].
>
>> Battersby wrote
>
>The equivalant product here in Texas is duoMatrix-G (gypsum + latex + resin
>+ hardener). There is also duoMatrix-C. I don't like it for about the same
>reasons you state.
[What's the difference between the G and C? Do you mix it with Densite
plaster instead of FGR 95? By the way, I tracked down some of this locally,
and I'm going to give it a try- the 100 lb sacks cost about the same as 50
lb sacks of FGR (but they have a $100 minimum.) ]
>
>> On the other hand, the tests I've
>> had out in the California weather (not "real" weather, I know) have shown
>it
>> to be remarkably durable outdoors, at least absent a lot of freeze/thaw.]
>
>Are these tests - raw, or sealed, or both??
[Raw. It seems to support a little black mildew in moist areas, but there's
none of the "Swiss-cheesing" one gets from regular plaster out in the rain.]
>
>Is AquaCast available out west yet??
[Yes- Douglas and Sturgess carries it. I got some, but haven't tried it
yet.]
>
>> >Michael Gainer wrote
>> Tufstone is very very nice,
>> >I agree with you on this Michael. This is a great product. Really
>> convenient
>> >that it comes in the bag already fibered, or unfibered. It pigments
>nicely,
>> >and I have found that it is extremely resistant to chipping.
>>
>> [I didn't realize it came unfibered. Does D&S carry it that way now, or
is
>> it a special order item? I agree, the convenience of a single-component
>> product has a lot to recommend it.]
>Why would you want unfibered TufStone Andrew??
>
>Battersby.
[Did I ever share my feelings about fiberglass with you? I prefer to add
aramid or graphite fibers myself to interior coats, instead of having to
deal with finely-divided fiberglass, which makes seams all fuzzy where
they're trimmed.]
Andrew Werby
http://unitedartworks.com
Michael Gainer
> >
> >Battersby.
>
> [Did I ever share my feelings about fiberglass with you? I prefer to add
> aramid or graphite fibers myself to interior coats, instead of having to
> deal with finely-divided fiberglass, which makes seams all fuzzy where
> they're trimmed.]
>
> Andrew Werby
> http://unitedartworks.com
The fiber in TufStone is *very* fine, a few mm long, and based
on appearance, it is some polymer, not glass. I've been working
with it both latex-gloved and bare-handed for a couple of years
now. I don't notice any difference between gloved and not,
beyond the usual chapping from plaster in general. More specifically,
I know what the dermal and pulmonary irritation from fiberglass
insulation is like, and I notice none of that.
You're right about fuzziness on sanding, but just going down in
grit to 200 or 400 takes most all of the surface fuzz right back off.
I've been meaning to see if a quick pass with a torch would vanish
the fuzz, but it's never been enough of a problem yet.
Battersby
> >The equivalant product here in Texas is duoMatrix-G (gypsum + latex +
resin
> >+ hardener). There is also duoMatrix-C. I don't like it for about the
same
> >reasons you state.
Andrew Werby wrote
> [What's the difference between the G and C?
Gypsum - Cement
> Do you mix it with Densite plaster instead of FGR 95?
FGR. I'm not familiar with Densite.
> By the way, I tracked down some of this locally,
> and I'm going to give it a try- the 100 lb sacks cost about the same as 50
> lb sacks of FGR (but they have a $100 minimum.) ]
Give us a report when you get a chance to evaluate. What's the difference,
besides the price?? Or do you know yet??
> >> On the other hand, the tests I've had out in the California weather
> >Are these tests - raw, or sealed, or both??
>
> [Raw. It seems to support a little black mildew in moist areas, but
there's
> none of the "Swiss-cheesing" one gets from regular plaster out in the
rain.]
So the tests are actually *out in the rain*.
> >Is AquaCast available out west yet??
>
> [Yes- Douglas and Sturgess carries it. I got some, but haven't tried it
Be sure to let me know what you think of it. It acts really different from
any others I use.
> >Why would you want unfibered TufStone Andrew??
> [Did I ever share my feelings about fiberglass with you?
No.
> I prefer to add
> aramid or graphite fibers myself to interior coats, instead of having to
> deal with finely-divided fiberglass, which makes seams all fuzzy where
> they're trimmed.]
I'm not familiar with either one of those fibres. so what?? They trim
cleaner?? Stronger??
Bb.
> Andrew Werby
> http://unitedartworks.com
ubg...@my-deja.com
<Sjle6.132494$df5.4...@news1.crdva1.bc.home.com>,>
> Lime plaster/concrete is a brilliant surface for painting fresco,
scratching
> a sgraffito, making delicate hand modelled ornaments, or making a
classic,
> beautiful wall or ceiling. For this reason its use will never die. The
> modern gypsums have, by in large, offered very little to the world of
> aesthetics - they quite rightly have been associated with the
Victorian era
> of overly fussy, weakly cast, interior ornament. Their use, or rather
abuse,
> has brought down the plaster trade and its old skills to its knees
Gary, could you explain the difference between lime plaster and the
modern gypsums? Do you think there would be any advantage to using
lime plaster for unique fine art casting? I've noticed that some
unpainted cast plaster sculpture from the 19th century--Rodin, for
instance--has a more aesthetic surface appearance than anything you can
get with today's gypsums, quite apart from the superior genius of
Rodin. A raw casting of a Rodin is quite satisfying and in some sense
a better replication of the original clay model than the final bronze,
as Rodin himself acknowledged. The older plaster seems brighter, finer
and denser, and I've often wondered what the difference might have been
in that material from what we have today. Do you think some of the
older casting was done with lime plaster?
Thanks for all the great info in this thread and others.
Bob
.
Andrew Werby
> I prefer to add
> aramid or graphite fibers myself to interior coats, instead of having to
> deal with finely-divided fiberglass, which makes seams all fuzzy where
> they're trimmed.]
I'm not familiar with either one of those fibres. so what?? They trim
cleaner?? Stronger??
Bb.
[No, but if you just use them in interior coats, they aren't there at the
surface to give you fits. The aramid (Kevlar) fiber is stronger and more
flexible than fiberglass, and if it does come to the surface a torch will
cure the fuzziness- or at least reduce it to stubble. Does anyone know what
fiber is used in Tuffstone? I assumed it was fiberglass, but if not, then
what is it?]
Andrew Werby
http://unitedartworks.com
Michael Gainer
> fiber is used in Tuffstone? I assumed it was fiberglass, but if not, then
> what is it?]
>
> Andrew Werby
> http://unitedartworks.com
USG's MSDS says "Ethylene Vinyl Acetate Polymer".
Gary Waller
There are castings in lime plaster (as per my link earlier in this thread)
and also documented throughout the ancient worlds (and I mean worlds as a
global term). The lime was typically not cast, but hand laid for
architectural walls, ceilings, and built up reliefs. The evidence is that
when lime plaster was cast it was not used in the modern sense. The mix
would be placed in a mold (usually rigid) and there is a magical point where
it becomes very plastic, at this point it would be slapped into place, I
assume also using a bit of fresh plaster as "glue", and then it was worked
in place - much more so than set hard plaster. The English tended to prefer
natural, organic forms and liked to "model" (build up) their designs, the
French preferred intricate shadow plays and liked to "carve" at the point
when the lime plaster carves like soft sandstone. The other feature of
casting "plastic" lime plaster is that it can soak in pigments which become
very permanent as the material "recarbonates" (lime plaster does not dry
like paint but has a long cure which relies on taking in carbon dioxide from
the air).
Again, as per the link, the modern thinkers tend to assume that lime plaster
was/is a type of mortar - ie three parts sand, one part lime putty. In fact,
this is tremendously versatile material - a wide variety of highly secretive
and original materials may be added to the mix - including gypsum and white
cement of course. To try to identify all these substances has been
troubling - for example they have no idea how much marble dust was/is added
to modeling/casting lime plaster because after 100 years all the putty
changes to the same fundamental ingredient as marble - calcium carbonate.
100 years is the benchmark where lime putty actually starts to become harder
and more durable than marble or limestone. It is more durable because its
crystals have not been fractured and stressed by the stone carver's work.
The number one enemy of lime plaster is acid rain - and the acidic skies of
Europe in the 1800's and 1900's did damage to exterior pieces and the
reputation(s) of lime plaster, marble and limestone. I have been
experimenting with various formulations and I am becoming very close to
perfecting a modern, lime based modeling/casting putty. As far as I know, I
am the only one even interested in reviving the old 'stucco duro' materials
and techniques for use in sculpted walls and ceilings.
Without checking my facts, I would suppose that Rodin would have used the
original "plaster of paris" which has probably been used up by now. A
modern, high calcite lime putty is brilliant white, is like soft butter, and
cures to an unbelievably hard surface, but is seldom used on its own. The
problem is that it can take up to a year breathing in carbon dioxide from
the air to obtain this rock hard status. To protect it from fingermarks (all
good sculptured works should attract caresses - even walls) it was/is coated
with beeswax or water glass (potassium silicate) which still allows
breathing. The 'cheaters' way is to add gypsum or white cement which gives
early strength but not the long term strength of lime - the idea is to
balance the two competing principles - and then paint/paper the wall or
casting. This solution was born from the fact that plasterers, sculptors and
painters all became separate trades, each trying to grab as much work as
possible for their craft/art.
[Gary, could you explain the difference between lime plaster and the
Andrew Werby
could be bent to conform to radiuses and irregularities, as was historically
done. This also sounds similar to the lime plaster used in fresco painting,
another almost-lost art. Is the modern version you're developing going to
have some polymer or something in it to repel the acid rain? I wonder if the
"carbonization" you mention could be accelerated by curing in a CO2
atmosphere. Is this formula something you're planning to share with the
rest of the world? Adding a little gypsum plaster, by the way, is a
tile-setter's trick for getting concrete to "kick" early- used in
moderation, I think it has little effect on ultimate strength, although it
may inhibit the plasticity you speak of.]
Andrew Werby
http://unitedartworks.com
Gary Waller wrote in message ...
Lauri Levanto
Some critics claim that architecture benefits when
the architect thinks in pathological units like inches and feet.
Fos us, who live about the other side of North Pole,
the Imperial system (The U.S. is hardly more democratic¨when
mearurings are concerned) is a real pain.
Can someone figure out
"If I melt 6 ounces of snow, how many fluid ounces water I get?"
* * *
Another concern is the brand names.
Most of us are happy when Forton MG or Hydrocal
is prescribed. Again here my local supplier
or the main importers have never heard of such names.
Can we try to give some descriptions, in addition to
brand names for recommended materials.
-well, I am aware that generic soapstone can be
almost anything but granite.
-lauri
Gary Waller
You make some good points. You should know, however, that Forton MG is a
Belgium based company, working with a British patent, it should be widely
available throughout EC? For the MG, try concrete additive suppliers - they
are more familiar with this company and its concrete polymers. This is a
company with over six hundred employees.
Andy Dingley
>water glass (potassium silicate)
I'd always understood waterglass to be sodium silicate. Is this
really a potassium silicate, used for this particular purpose ?
I wonder if a calcium silicate is usable ?
(I'll consult the tame chemist)
On a related topic, do you know what English pargetters used as a
limie-based plaster ?
(Pargetting is a relief moulded decorative plastering found on the
outsides of buildings in SE England, from Tudor times onwards)
--
Do whales have krillfiles ?
Gary Waller
Gary Waller
There is a whole family of silicates, and yes, sodium silicate is the most
well known and easiest to work with. Unfortunately it is not as durable as
the potassium silicate. It is for this reason that Keim mineral paints
chooses to use it as their paint "base". The pigmented water glass is used a
lot in Europe, just starting in North America, I don't know the best website
but one I mentioned previous www.linerol.com has links.
Pargetting uses a standard lime mortar - ie lime putty and sand - and I
think it is about time that the artistic stucco work of the past came back.
Exterior stucco has become so boring - monolithic shades of pastel color. Do
you know about sgraffito stucco? This is where you scratch away multicolored
layers of plaster to make a graphic design. One of the most famous artists
was Heywood Sumner of the U.K.
http://www.stmary-greatwarley.org.uk/maryhist.htm and an example in the USA
http://freenet.buffalo.edu/~pacb/projects/graycliff/ Its an incredible
effect, but most sgraffito in modern times were for advertising and signage,
much simpler. Unlike paint, sgraffito will improve with age and aquire an
architectural patina.
Get scratching!
Gary
Akilli
Just figured I would answer the nagging question of calcium silicate:
When sodium silicate is applied to a material such as limestone or stucco, the
calcium in the stone switches places with the sodium, and forms an insoluble
compound - calcium silicate. It is this property which allows water glass to be
used as a consolidant for rotting limestone, concrete etc., and fixes pigments
when used as a paint.
If as a kid, you ever bought these "magic" crystals, which when dropped
into water, formed tenuous colored castles, it was this reaction at work.
They're still quite entertaining.
Ethan Gross
Andy Dingley
>Hi Andy - good to see you online again!
Thanks 8-)
>Do you know about sgraffito stucco?
Oh yes. Can't recall seeing any in the UK, but if you go to central
Europe (esp. Prague) it's all over the place -- usually trompe l'oeil
stonework.
Apacheforge
Just figured I would answer the nagging question of calcium silicate:
When sodium silicate is applied to a material such as limestone or stucco, the
calcium in the stone switches places with the sodium, and forms an insoluble
compound - calcium silicate. It is this property which allows water glass to be
used as a consolidant for rotting limestone, >>
Just an aside, I remember my grandmother telling me that they would store eggs
in a crock of water glass
in the root cellar through the winter (chickens dont lay in winter under free
range conditions). Always wondered how this preserved them.Rufo
Gary Waller
How do you do blowding up those big boulders! You could make that a webcast.
Have you ever seen that English sculptor who blows up metal panels into (I
believe) plaster dies? He makes a big production out it - great for public
art. Apparently this a highly cost effective way of molding aluminum and
other lightweight metals - once you get around to your blasting license,
etc.
You could practise metal artwork and blow up your rocks all at the same
time.
If any of your grandmothers eggs are leftover, they should be about ready
to blow up too.
Gary
Lauri Levanto
explosives,
http://www.fng.fi/cgibin/art.pl?en_home_artist_empty_empty_lpulline_all=lpulline&w=N0092800&w=N0091400&w=N0095800&version=html4#first
At Helsinki Airport she has a wall panel, something like 4x8 yards explosive
formed
copper.
The Rautaruukki factory near my town produces endplates for pressure conteiners
with explosive method. They can forge that way 1" steel into a mold in one
blast.
-lauri