Shellac help?
PMF
I'm working on a pair of oak/walnut end tables and have a couple of
finishing questions. My plan is to give the tables a couple of wash
coats of 1# garnet shellac to enhance the grain and give the wood a
slightly darker tone. Since these are end tables and I can't guarantee
that all my friends and family are coaster-trained, I want to apply
something more water resistant over the shellac.
Here begins the questions...
I've read that most polyurethanes cannot be applied over shellac unless
it's dewaxed. Why? Is it just less durable or will it shed it like a
lizard? (I assume that my Behlen's A.C. Garnet shellac is not
dewaxed...) What if I wiped the shellac down with naptha before
applying a poly? (Oh, well, I thought I'd ask)
What *can* you apply over shellac? I understand Behlen's "Rock Hard
Tabletop Finish" can be applied over shellac. Is this stuff a natural
varnish instead of a polyurethane, and is that what makes the
difference? Has anyone used that stuff, and what did you think?
Am I just asking for trouble? Part of me thinks I should just use
shellac without a topcoat, but that would require me to become a Fascist
Coaster Czar. I understand that shellac is easily repaired, but I would
rather not have to repair it in the first place.
I can't resist the "old school" allure of coating my creation with
golden bug secretions, but I want a durable finish. What should I do?
-Patrick
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PMF <pmfr...@my-deja.com> wrote:
> What *can* you apply over shellac?
Ummm.... More shellac....
> Part of me thinks I should just use shellac without a topcoat,
Or several coats of Shellac.
> but that would require me to become a Fascist Coaster Czar.
Contrary to popular belief, dewaxed shellac is quite water resistant.
(this is why shellac-coated pills don't melt in your mouth, but they do
in your stomach.)
> I can't resist the "old school" allure of coating my creation with
> golden bug secretions, but I want a durable finish. What should I do?
Go read here:
http://www.concentric.net/~Odeen/oldtools/shellac/info.shtml
--
John
And all the Wookies say:
"He's pretty fly, for a Jedi."
Russ Ramirez
PMF <pmfr...@my-deja.com> wrote in message
news:7qenrh$7v4$1...@nnrp1.deja.com...
snip...
> I've read that most polyurethanes cannot be applied over shellac unless
> it's dewaxed. Why? Is it just less durable or will it shed it like a
> lizard?
Yes it will.
> (I assume that my Behlen's A.C. Garnet shellac is not
> dewaxed...) What if I wiped the shellac down with naptha before
> applying a poly? (Oh, well, I thought I'd ask)
No it's not de-waxed, and wiping with naphtha does not hurt anything, but it
won't help the situation, the wax is in solution. You can mechanically
separate the good from the 'bad' by letting a sizable quantity, i.e. a pint
or more, sit until the wax settles and decanting off the good stuff. (Then
buy de-waxed shellac for next time).
>
> What *can* you apply over shellac? I understand Behlen's "Rock Hard
> Tabletop Finish" can be applied over shellac. Is this stuff a natural
> varnish instead of a polyurethane, and is that what makes the
> difference? Has anyone used that stuff, and what did you think?
>
Over de-waxed shellac almost all coatings can be applied, except for those
contain solvents, reducers, or plasticizers that will burn the shellac - but
most of the latter you probably won't or can't buy. I still wouldn't put
Rock Hard over regular shellac, although the results would probably be
better than using an oil-based varnish made with poly resins. Poly resin
varnishes generally don't stick well to what they 'see' as a smooth surface
or anything like the shellac that repels the oil film somewhat. Waterborne
poly finishes can actually burn the shellac so bad that the result with
brush application will be uneven coloring and something looking like
fisheyes if sprayed. So natural resin oil-based varnishes 'stick' better,
but you're still risking a failure down the road. Sometimes the failure even
occurs right after sanding the first coat over regular shellac.
> Am I just asking for trouble? Part of me thinks I should just use
> shellac without a topcoat, but that would require me to become a Fascist
> Coaster Czar. I understand that shellac is easily repaired, but I would
> rather not have to repair it in the first place.
>
Actually de-waxed shellac is quite water resistant by itself. A final buff
with paste wax helps even more. Quite often a minor white ring or 'blush'
will go away by itself. It depends upon how much protection you practically
need - I'd worry more about a 151 and coke more than water from a sweaty
glass due to the alcohol. Since your not dealing with a bar top, all-shellac
is fine. On the other-hand if you don't have a lot of experience putting
down a large number of thin coats of shellac, I would practice on something
else first.
> I can't resist the "old school" allure of coating my creation with
> golden bug secretions, but I want a durable finish. What should I do?
>
> -Patrick
>
Well, protection and aestetic appeal sometimes run opposed to each other
with DIY coatings, but there are plenty of professional coatings that
achieve both kinds of results. You could do what my mother did in the 60's
with her (shellac'd) end tables - get some glass made for them.
jim mcnamara
1. you can dewax shellac yourself. Just let it sit undisturbed for 3-4
days, then decant off the clear (dewaxed) shellac and pitch the cloudy
(waxy) stuff at the bottom
2. Polyurethane will adhere to dewaxed SHELLAC - just fine.
You can also apply poly w-b products over dewaxed shellac.
Be sure to abrade the shellac lightly with 320 grit first.
3. dewaxed shellac is water resistant - not waterproof. It just can't deal
with alcohol, at all. Shellac was used for years as a floor finish. It
worked just fine, thank you.
4. don't believe all of what manufacturers put on can labels about their
products - other than recommended application schedules and whether it's an
exterior or interior finish. They would have us believe that exactly what
we need is in their can - nowhere else. For example, lacquer manufacturers
found out they could sell more product by having finishers buy a 'system' -
proprietary sealer to go under the lacquer- this happened in the 60's. The
hype and subsequent confusion has gotten lots worse since then.
To answer a question or two -
Poly is notorious for poor interfilm adhesion - to itself or other films
sometimes. Roughing up old varnish or anyother film improves adhesion a lot.
Poly is very tough and fairly close to waterproof. It resists most
household chemicals. Shellac doesn't do that- alcohol and ammonia can ruin
it.
Behlen's Rock Hard is a lot better for film-to-film adhesion - at least as
far as varnishes go.
There isn't any such thing as a 'natural' varnish - unless you mean
something like violin varnish - which is no more water resistant than
shellac. Modern Varnish (1885 on) is made by heating a drying oil (like
linseed oil) with some kind of resin (manmade) - the result is a complex
chemical 'mess' that hardens on exposure to air.
Voilin varnish is amber, copal, balsam, maybe shellac (plus solvents) - all
natural resins. The words we use for finish like 'varnish' and 'lacquer'
have acquired lots of different meaings over the years to the point of total
confusion when talking about something from 150 years ago. Violin varnish is
actually a lacquer, as is shellac.
For any varnish, thin the product about 10% with the appropriate thinner.
This gives far better flowout (reduces brushmarks and other blems).
Behlen's Rock Hard requires proprietary finish (it actually does...) if you
want it to retain it's curing time.
Poly is not reparable, generally. Do not assume that it won't need repair.
It will. Someday. If you apply poly, it won't be any better against gouges
and dropped items than shellac, it just usually cannot be repaired very
well. Shellac can be repaired. You can sometimes repair a gouged poly film
with padding lacquer (a shellac based product)
There is no one perfect film finish. You gain water and chemical resistance
with poly and get loss of reparability.
It also does not rub out nearly as well as shellac or lacquer.
Trade-offs....
jim mcnamara
Gerry Glauser
<snip>
>I've read that most polyurethanes cannot be applied over shellac unless
>it's dewaxed. Why? Is it just less durable or will it shed it like a
>dewaxed...) What if I wiped the shellac down with naptha before
>applying a poly? (Oh, well, I thought I'd ask)
repaired.
>
>What *can* you apply over shellac? I understand Behlen's "Rock Hard
>Tabletop Finish" can be applied over shellac. Is this stuff a natural
>varnish instead of a polyurethane, and is that what makes the
>difference? Has anyone used that stuff, and what did you think?
1- Lacquer (haven't tried this combination)
2- Dewaxed shellac
3- Glass
While the glass would be the most durable and easiest to repair (replace), you can also
extend #2 a bit. If the finish is well leveled, and isn't already too thick (or sand a
bit), then add two coats of 1# dewaxed shellac. Apply it properly by flowing it on, and it
should seal nicely. At that point, scuff sand with 400 grit and clean well. Finally, apply
two thin coats of poly. This could be thinned oil base (slightly more durable) or water
base poly (my preference).
>Am I just asking for trouble? Part of me thinks I should just use
>shellac without a topcoat, but that would require me to become a Fascist
>Coaster Czar. I understand that shellac is easily repaired, but I would
>rather not have to repair it in the first place.
Well, you could always try the first part of #2 above. The dewaxed shellac will be much
more resistant to spills and such. Frankly, I'd go that route and see how it worked out.
You can always go back and add the poly later, if needed.
>
>I can't resist the "old school" allure of coating my creation with
>golden bug secretions, but I want a durable finish. What should I do?
Other than places where I might spill solvents, I've replaced poly with dewaxed shellac on
all jigs and fixtures in the shop, and it's been holding up very well.
>-Patrick
Gerry Glauser
Just a slight clarification on a minor point, please.
I assume your poly references here are to regular shellac, and I agree with the "fisheye"
type look when sprayed and other comments. My only question is your reference to burning
the shellac. I don't understand what you mean by that. IMO, the shellac would survive
quite nicely, unlike the poly, and I'm not aware of it being effected at all here.
--Gerry Glauser
On Mon, 30 Aug 1999 16:25:03 -0500, "Russ Ramirez" <m...@my.computer> wrote:
<snip>
Russ Ramirez
The polyols like glycol ethers and monobasic alcohols in something like
Minwax Polycrylic for example will burn the shellac when used over top of
it, meaning simply dissolving it to some degree. The term is commonly used
to describe what happens when you apply a subsequent coat of shellac too
soon over an existing coat or when clarifying a French polished surface (to
remove the oil residue) and you accidentally re-dissolve part of the
surface (followed by a lot of yelling). Really, I don't recommend that folks
use shellac as a 'colorant' per se, a stain or dye can be adjusted to
produce any color that shellac will. If that special chatoyance that shellac
produces is desired, then use ONLY shellac. Yada, yada...
Russ
Gerry Glauser <ger...@cisco.com> wrote in message
news:37d043f0...@news.cisco.com...
Russ Ramirez
employed a form of natural resin, and usually were alcohol or 'spirit'
soluble - hence the name. Some texts also refer to varnishes made with
resins soluble with turpentine, such as rosin(colophony) or dammar as
'spirit' varnishes as well. Spirit varnishes, including shellac, were always
in any case evaporative coatings. When these spirit varnishes were combined
(mixed) or cooked with oil, they were often referred to by specific uses
such as carriage, violin, etc. varnishes. Eventually someone discovered that
several of the natural resins required 'running' before they would dissolve
efficiently. This discovery, along with ways to improve linseed oil prior to
cooking, led to varnishes being thinned with turpentine *after* they were
cooked. Same ingredients, but a different process. What we now call varnish
is essentially this latter product, and as Jim said, the resins used in the
recipe may be synthetic. Upon further trial and error research, folks
discovered that Tung oil made a superior oil-based varnish. For a while
Oiticica oil was used when Tung oil prices got out of hand in the 1930's.
<commercial>
Today we have a product available called Waterlox Transparent, or just
Waterlox, that is made using the knowledge gained in the 1800's through the
turn of the century. Waterlox is cooked in open kettles and contains Tung
oil, fossil resins (like congo copal), ester gums, and phenolic resin (the
synthetic resin of the bunch).
</endcommercial>
Russ Ramirez
jim mcnamara <csi_...@coopserv.com> wrote in message
news:7qetpq$q3k$1...@sloth.swcp.com...
>snip...
> There isn't any such thing as a 'natural' varnish - unless you mean
> something like violin varnish - which is no more water resistant than
> shellac. Modern Varnish (1885 on) is made by heating a drying oil (like
> linseed oil) with some kind of resin (manmade) - the result is a complex
> chemical 'mess' that hardens on exposure to air.
>
> Voilin varnish is amber, copal, balsam, maybe shellac (plus solvents) -
all
> natural resins. The words we use for finish like 'varnish' and 'lacquer'
> have acquired lots of different meaings over the years to the point of
total
> confusion when talking about something from 150 years ago. Violin varnish
is
> actually a lacquer, as is shellac.
> snip...
Paul T. Radovanic
Thanks for the clarifications, Jim.
>Behlen's Rock Hard is a lot better for film-to-film adhesion - at least as
>far as varnishes go.
Yeah, I've used it over dewaxed shellac many times and never had any
problems.
>
>For any varnish, thin the product about 10% with the appropriate thinner.
>This gives far better flowout (reduces brushmarks and other blems).
>Behlen's Rock Hard requires proprietary finish (it actually does...) if you
>want it to retain it's curing time.
I think you meant to say "proprietary solvent" here. Rockhard's
special solvent lists "Stoddard solvent", and so does Waterlox. What
is Stoddard solvent, anyway?
Paul Rad
>
Russ Ramirez
called ASTM D 484 testing requirements, and have a *minimum* flash point of
100 degrees F. I believe this spec was originally put into place for MS to
be used in dry cleaning.
Russ Ramirez