A question on making ground glass...

[Mark Sawyer]

I've been doing my homework getting ready to make a ground glass or two, and have a question. It's popular for people to use a smaller square of glass to grind the ground glass, using aluminum oxide as the grinding compound. But I was curious... if one used a 5x7 piece of glass to grind another piece of 5x7 glass, would one end up with two serviceable 5x7 ground glasses? Enquiring (and lazy) minds want to know...

[Ari]

I am no expert, but I think you could end up with two 5x7 screens.
All you have to do is maintain perfect, constant and even pressure on the entire surface of both screens...all the time.
You will get one good screen and one almost-done screen; you can just go back and grind the missing areas of the second screen, which should take much less time.

[Andrew O'Neill]

Logic says yes.

[Mark Sawyer]

Logic says yes.

"In theory, practice and theory are the same thing. In practice, they aren't."

~ Yogi Berra

[cowanw]

Not so easy to get a good grip and side to side and downward push on a flat piece of glass, without gripping the edges and cutting yourself. A glass puck or in my case a juice glass with a heavy bottom fashionable 29 years ago worked well as a dedicated tool. No matter if the bottom of the glass isn't flat or smooth it soon will be.

[Mark Sawyer]

Good point. I may need to attach a handle with removable silicon or something.

And I expect Ari's right, one screen (or both) may need a little touch-up. Or it may be best using a 4x5 to polish a 5x7 or 8x10. It will be an experimental process...

[Jim C.]

I'd try spray cementing a rubber pad like a mouse pad or yoga mat to a flat board ( melamine coated MDF )
that has a decent handle on it to use on the glass, you'll get a better grip and for pressure, you can place weights
or a sand bag on top.

I had thought of something I came across that I can't remember what it was called, it had a pretty good grippy surface but
wasn't really sticky. I remembered - rubber shelf liner or router pads.
I also thought of suction cups but depending on the thickness you're using it may bow the glass.

[Tin Can]

I have made 5 GG's and taught 2 people do it it. I do not suggest using 2 pieces of identical glass at once. You will find localized unground areas as you check your work in the sink, by completely washing off the grit. Window glass is wavy and needs to be ground flat. Be very careful as you move to small grits to not contaminate with larger grits as you will make scratches.

I use a 3x3" 1/4" piece of glass for the puck, and it gets better with use, and thinner! I use only my fingers to grip the puck. I watch a movie and I'm done.

Crack off the corners first.

I use glass from Home Despot, very cheap and 8X10 and 11X14 is sized perfectly.

I recently bought a 4X5 Satin Snow GG here, just to see how good it was. It is not as good as Steve Hopf's and I have bought 3 of them. I hope to achieve his results one day...

I compare GG's first by looking at a bright light with them held in my hand, then mounted in the camera.

[Jody_S]

I think you will find it impracticable unless you use a large quantity of very liquid AlO slurry. With smaller, denser pastes, the two glass surfaces stick together, and 2 5x7 glasses will possibly break from the suction at some point in your grinding.

[Tin Can]

I think you will find it impracticable unless you use a large quantity of very liquid AlO slurry. With smaller, denser pastes, the two glass surfaces stick together, and 2 5x7 glasses will possibly break from the suction at some point in your grinding.

+1.