acid etched vs sand blasted GG
monochrome
etched ground glass? Are there advantages/disadvantages to each? Either
one brighter viewing or better contrast? thanks
Sandy King
<victor....@verizon.net> wrote:
Acid etched glass usually has a finer surface than that made by normal sand
blasting. This results in a brighter screen that allows one to focus on
fine detail, with a central bright spot. A ground glass made from sand
blasted glass is typically somewhat darker and has less detail (but perhaps
better contrast), and overall illumination is somwhat better.
However, be aware that great variations are possible with either type of
ground glass as it is possible to make a very coarse screen by repeated
etching, or a fine screen with blasting by using very fine grit.
Sandy King
Richard Knoppow
I've found the opposite. The coarser the glass the hotter the
centeral spot and dimmer the corners. The finer the surface grain the
closer it comes to being a Lambertian surface, that is, a perfectly
diffusing one. If the surface is too fine the image will be dim and it
may be hard to focus on because of the very diffuse surface.
I have samples of ground glass of various finesses but have no idea
of what method was used to make them.
There are three methods. Sand blasting, etching with hydroflouric
acid (really nasty stuff), and grinding using grit and a second flat
plate. Ground glass is not too hard to make using the grinding method.
Good ground glass of the right texture is available from Edmund
Scientific at quite reasonable prices.
---
Richard Knoppow
Los Angeles, Ca.
dick...@ix.netcom.com
Sandy King
wrote:
> I've found the opposite. The coarser the glass the hotter the
> centeral spot and dimmer the corners. The finer the surface grain the
> closer it comes to being a Lambertian surface, that is, a perfectly
> diffusing one. If the surface is too fine the image will be dim and it
> may be hard to focus on because of the very diffuse surface.
> I have samples of ground glass of various finesses but have no idea
> of what method was used to make them.
> There are three methods. Sand blasting, etching with hydroflouric
> acid (really nasty stuff), and grinding using grit and a second flat
> plate. Ground glass is not too hard to make using the grinding method.
> Good ground glass of the right texture is available from Edmund
> Scientific at quite reasonable prices.
> ---
> Richard Knoppow
> Los Angeles, Ca.
> dick...@ix.netcom.com
I am comparing sand blasted frosted glass (fairly coarse) purchased at a
local glass store to acid etched glass I made with the product Armour Etch,
in two sizes, 7X17 and 12X20. The acid etched glass is much finer and
brighter than the sand blasted glass. However, there is no question but
that when looking at the image on the ground glass from a distance of about
10-14" the fine screen (acid etched) has a distinct bright center spot but
illumination falls off significantly toward the corners. The coarse screen
(sand blasted), though not as bright, has better overall illumination.
In experimenting with different kinds of ground glasses I have even acid
etched glass previously sand blasted. This gives a very nice groundglass,
with excellent overall illumination and eveneness, though with somewhat
coarse detail.
Sandy King
Sandy King
John
wrote:
>In experimenting with different kinds of ground glasses I have even acid
>etched glass previously sand blasted. This gives a very nice groundglass,
>with excellent overall illumination and eveneness, though with somewhat
>coarse detail.
>
>Sandy King
>
Ever try just blasting the corners ? I'd imagine that the overspray
would take care of any edges.
Regards,
John S. Douglas Photographer
http://www.photographers-darkroom.com
===============================
Sandy King
<jo...@photographers-darkroom.com> wrote:
> Ever try just blasting the corners ? I'd imagine that the overspray
> would take care of any edges.
>
> Regards,
>
> John S. Douglas Photographer
> http://www.photographers-darkroom.com
> ===============================
The purpose of further acid etching of the coarse sand blasted surface was
to smooth it out and improve brightness. The idea was based on the fact
that if you wet out a very coarse ground glass it will be much brighter. A
light coat of clear varnish or polyurethane will achieve the same purpose.
As for your suggestion about blasting the corners, sorry, I don't
understand what you are suggesting.
Sandy King
John
On Tue, 22 May 2001 11:59:34 -0400, san...@hubcap.clemson.edu (Sandy King)
wrote:
>The purpose of further acid etching of the coarse sand blasted surface was
>to smooth it out and improve brightness. The idea was based on the fact
>that if you wet out a very coarse ground glass it will be much brighter. A
>light coat of clear varnish or polyurethane will achieve the same purpose.
>
>As for your suggestion about blasting the corners, sorry, I don't
>understand what you are suggesting.
>
>Sandy King
Well actually I was thinking that you etch with the acid first and then
use the blaster to frost the corners so that the bright center does not get to
be too coarse.
And are you using a sand blaster or a glass beader ?
Sandy King
<jo...@photographers-darkroom.com> wrote:
> Well actually I was thinking that you etch with the acid first
and then
> use the blaster to frost the corners so that the bright center does not get to
> be too coarse.
>
> And are you using a sand blaster or a glass beader ?
>
> Regards,
>
> John S. Douglas Photographer
> http://www.photographers-darkroom.com
> ===============================
There are two kinds of glass in question. One is the sand blasted material
that is available already frosted and cut to the required dimension.
Another is a plain sheet of glass that *I* etch with Armour Etch, a
flurocarbon etching material.
The sand blasted material works fine, but is coarse. The acid etched
material is smooth but tends to be unevent. Etching the previously sand
blasted material gives a glass with a useful compromise of overall eveness
and smoothness.
Sandy King
Peter De Smidt
> local glass store to acid etched glass I made with the product Armour
Etch,
> in two sizes, 7X17 and 12X20. >
>
Sandy,
How did you manage to get an even 'etch' using the acid? I've tried
numberous methods, and while the glass produced was usable, it was quite
uneven.
Peter
Sandy King
<pdes...@fdldotnet.com> wrote:
Peter,
I have etched glass on several ocassions and have to agree that it is
difficult to get it right. The first time I tried it about 5 years ago was
a disaster. However, recenlty I saw a really smooth piece etched by a
friend and was inspired to tried it again, having just broken my ground
glasses on both the 7X17 and 12X20 cameras. This time I have gotten some
very nice results. Here is what I do.
1. First, make sure the glass to be etched is clean. Scrub it well with
some kind of degreaser and then allow to dry completley.
2. Mask with 2" wide tape (I use the blue masking tape) the edges of the
back of the glass to prevent unwanted etching on the smooth side from acid
spill-over.
3. Stir the contents of the container of Armour Etch well.
4. Apply a very thick coat of the paste. Apply first in the long dimension,
repeat for the short dimension. Leave for about 10-15 minutes, then wash
everything away, using a stiff brush, as quickly as possible.
5. If there are any areas of uneveness repeat the process one or more
times. With 2-3 coatings I have had no difficulty getting a very even
etching.
Wear gloves with Armour Etch and wash it all away so so children or animal
have a chance to touch/ingest it as it is a dangerous material.
Regards,
Sandy King
5.
John
wrote:
>There are two kinds of glass in question. One is the sand blasted material
>that is available already frosted and cut to the required dimension.
>Another is a plain sheet of glass that *I* etch with Armour Etch, a
>flurocarbon etching material.
>
>The sand blasted material works fine, but is coarse. The acid etched
>material is smooth but tends to be unevent. Etching the previously sand
>blasted material gives a glass with a useful compromise of overall eveness
>and smoothness.
>
>
>Sandy King
Evidently I need to clarify what I was suggesting. Sorry for the
confusion.
What I was wondering was have you tried blasting the corner areas of the
glass _after_ acid etching the glass overall ? This would provide a greater
texture to the glass the further you get from the center . IMO this would
provide better illumination evenness.
Sandy King
<jo...@photographers-darkroom.com> wrote:
> Evidently I need to clarify what I was suggesting. Sorry for the
> confusion.
>
> What I was wondering was have you tried blasting the corner areas
of the
> glass _after_ acid etching the glass overall ? This would provide a greater
> texture to the glass the further you get from the center . IMO this would
> provide better illumination evenness.
>
> Regards,
>
> John S. Douglas Photographer
> http://www.photographers-darkroom.com
> ===============================
Hi John,
Thanks for the clarification. I did not understand your original comment
about this, as you could tell from my response.
The answer is no. I do not have the equipment to sand blast glass so to
this point all of the frosted glass that I have used has been bought over
the counter. On the other hand this sounds good in theory and I know some
custom glass workers and might ask them to put the experiment to the test.
Regards,
Sandy King