Sources for High Quality Ground Glass

[Drew Wiley]

Per acrylic in general : it's soft and easily scratched, it can bow and not remain flat, and
it's electrostatic and will inherently attract dust. One the plus side, it's hard to break and
a better temp insulator, so less prone to condensation fogging. You can help the static
issue somewhat with antistatic sprays.

[David Karp]

I bought a 5x7 GG from Steve Hopf. I like it a lot. He seems to be a very nice guy. I also have a Satin Snow, which is nice, but by way of comparison, I like the Hopf Glass better. For one thing, he offered the borosilicate glass option, which is stronger than regular plate glass. He also puts a nice grid on the glass if you like that.

[cyberjunkie]

I've been using some nice thin glass from surplusshed that works very well for making screens for small classic German folders, which require a very thin screen. It might be too thin for 8x10 though (although it would be very light).

http://www.surplusshed.com/pages/item/m3012.html

Surplus Shed also sold original Eastman Kodak ground glasses.
They are cheap and surprisingly good.
I purchased some, in 4x5, 5x7 and 8x10 inches, and i regret i didn't buy more.
I checked a few days ago, but the items have a different description, so i am not 100% sure that it is the same stuff.
I took advantage of the discount days (31%, IIRC), ordering some more, along some packs of much needed optical hardware (some tools, non-metric screws, bolts, nuts, nylon set screws, etc).
If the ground glasses presently on sale are of the same quality of the old ones, they win hands down in quality vs price.
A DIY glass COULD be a little cheaper, if you find the aluminium oxide locally.
Getting the two grades of oxide via mail order, and buying a sheet of good glass, makes you very close to what you'd pay to SurplusShed... provided you don't have to grind many glasses.
The compound used to grind engine valves could be easier to find, and could be even free (if you have a friend who repairs auto/moto/truck engines), but i don't think it would work so well..

My experience with custom/expensive ground glasses is very limited, but i recognize that the GG with integrated fresnel that came with my Tachihara is much better than the average glass found on pre-WWII cameras.
Though i don't agree with the notion that "newer is always better".
When i bought my Calumet C1, the GG broke just before shipment. The seller replaced the broken original GG with a Boss Intenscreen, which had a much higher commercial value.
I am not saying it is bad, it has some evident advantages, though i think that sooner or later i will replace it with one of those SurplusShed glasses, because they are a good compromise and i'm used to them.
IF/WHEN a fresnel is needed, there is the simple option of sticking (or holding) a reading glass fresnel on top of the GG, and quickly removing it when you are done. BTW, wide angles are NOT Calumet C1's cup of tea... so a fresnel isn't the most needed accessory

These are just personal experience, maybe not even worth the time i am spending at the keyboard. Though i think i have a small advice for your consideration:
before spending good money in a top product, you must know WHY you need it.
The first step in the right direction is to try a cheap-but-good product, and see by yourself if you REALLY miss something.
If you do, how much are you willing to pay for that extra?
The Eastman Kodak ground glasses i got from SurplusShed are a good starting point. They are incredibly better than those dark, milky glasses found on many antique cameras, but they are not on par with the best ones, which sell for much more.
Of course paying or not the premium is up to you, the decision should be largely dependent on your picture-taking habits (that is, the lighting conditions you usually find when shooting pictures).

have fun

CJ

[jose angel]

Per acrylic in general : it's soft and easily scratched, it can bow and not remain flat, and
it's electrostatic and will inherently attract dust. One the plus side, it's hard to break and
a better temp insulator, so less prone to condensation fogging. You can help the static
issue somewhat with antistatic sprays.

My main problem with them is about bow... the ones I have used even in 4x5" (from a well known first brand and very expensive) were useless. My advice is to keep away from plastic screens.

I work in a laboratory, we use pure aluminun oxide (corundum) in several grain sizes. It is easily available. The size of the grain provides a deeper or shallower surface; as Ian says, the difficult thing is to know which grain suit your needs. FWIW, grain sizes between 0.25um (500 mesh) and 250um (60mesh) are quite common.

[wiggywag]

My main problem with them is about bow... the ones I have used even in 4x5" (from a well known first brand and very expensive) were useless. My advice is to keep away from plastic screens.

I work in a laboratory, we use pure aluminun oxide (corundum) in several grain sizes. It is easily available. The size of the grain provides a deeper or shallower surface; as Ian says, the difficult thing is to know which grain suit your needs. FWIW, grain sizes between 0.25um (500 mesh) and 250um (60mesh) are quite common.

Interesting to consider the grain size. What would you consider being the best grain size? Is it harder to focus if the grain size becomes to fine?

[jb7]

Per acrylic in general : it's soft and easily scratched, it can bow and not remain flat, and
it's electrostatic and will inherently attract dust. One the plus side, it's hard to break and
a better temp insulator, so less prone to condensation fogging. You can help the static
issue somewhat with antistatic sprays.

If you were describing Polycarbonate I'd have to agree with you about the fact that it's soft, easily scratched, subject to bowing, and lacking flatness. Polycarbonate can be supplied as a substitute for acrylic if the correct specification is not adhered to, and unless you know the difference, you might conclude that the material supplied as Acrylic is unsuitable.

Cast acrylic, in the appropriate thickness for the size required, is flat and stiff, and harder and more durable than Polycarbonate. Providing it has been correctly stored prior to supply it is as flat as glass, and should maintain that flatness after installation in a camera.

[Joe Forks]

Smaller grain is easier to focus, but it takes longer to grind the screen with smaller grain. So you start say a 5 micron grain and grind for a while, then switch to a 3 micron grain to finish it up. Makes a really nice ground glass.

http://www.largeformatphotography.in...lass-yesterday

[IanG]

Interesting to consider the grain size. What would you consider being the best grain size? Is it harder to focus if the grain size becomes to fine?

As Joe says as well it's best to grind with a coarser grit first, 400 grit is ideal ,and finish with 600 grit this gives a mix of grain size and a better alround screen. I make a lot of screens and there's no reason why a home made screen can't equal ant commercial offering. All the screens I male are significantly brighter than the old Kodak and Graflex screens.

Ian

[C. D. Keth]

Smaller grain is easier to focus, but it takes longer to grind the screen with smaller grain. So you start say a 5 micron grain and grind for a while, then switch to a 3 micron grain to finish it up. Makes a really nice ground glass.

http://www.largeformatphotography.in...lass-yesterday

Note that a finer glass will be trickier to use with wide lenses because the hot spot will be a lot more pronounced than with a courser glass. This of course won't matter if you don't care for wide lenses or use a fresnel.

[Tim Meisburger]

Ian, can you give a us a note on your technique? Are you using loose grit, or sandpaper?