Made a ground glass yesterday.....

[Joe Forks]

Out of necessity - The ground glass on my 12x20 broke during shipment.... it was packed plenty good, but it was just one of those things, oh well.

So I checked out the listing for 12x20 ground glass.... huh? Nada!

Alright, I checked out that ebay seller with the high marks....... available but how much? Ouch, it's $1/sq. in for float and $2/sq in for borosilicate..... so $240 or $480 for a 12x20 ground glass?----- HAHAHA! I don't think so.

enter D.I.Y.
First I read this page
http://www.dokasphotos.com/techniques/ground_glass/
Sounds easy enough right? Well it is easy, it just takes time and elbow grease.

I got my supplies here;
http://www.willbell.com/ATMSupplies/ATM_Supplies.htm

Get the white al oxide lapping powder in 3 and 5 micron size (I got 1lb each, way too much material but what the heck)..... I also got the cera-hex-tool for $9.

Then you just sit down in front of work surface and start grinding. - Well I had to build the grinding tool first but that was pretty easy. The hard part is grinding to the very edge, it might work better to grind first then cut to final size, but if you break it wrong you waste a lot of time.

It turned out great...really really nice, and bright, even using soda lime glass. I'm going to grind another as a spare since I had two blanks cut.

I'd like to experiment with borosilicate glass but it's really expensive, so maybe in the future.

Here's a couple photos, I'll post the finished product later.

[BetterSense]

What kind of grinding tool is that?

I reground my 4x5 glasses with 400 grit SiC. For a grinding tool, I bought a $3 2x3" picture frame at Hobby lobby; it was one of those ones that is basically 2 sheets of thick glass that you are supposed to slide your picture in between. It was easy to pry apart and yielded 2 pieces of 2x3" by about 10mm thick glass.

[Joe Forks]

It's called a cera-hex-tol - what ever that is. Check the Willmann-Bell link, it's at or near the bottom of the page. They send you a ton of those little hexagons for $9. You use some epoxy and a small piece of tile to put the tool together with channels in between. Channeled tools are more efficient grinding tools, so they say!

[bsimison]

It's called a cera-hex-tol - what ever that is. Check the Willmann-Bell link, it's at or near the bottom of the page. They send you a ton of those little hexagons for $9. You use some epoxy and a small piece of tile to put the tool together with channels in between. Channeled tools are more efficient grinding tools, so they say!

Do you think the hexagon grinding tool worked better than using a smaller piece of glass as the grinding tool, like the online grinding tutorials recommend?

[Joe Forks]

Brett,
Purely speculation on my part, because this was my first experience, but having qualified my opinion I think absolutely it (should) work better.

[bsimison]

Brett,
Purely speculation on my part, because this was my first experience, but having qualified my opinion I think absolutely it (should) work better.

Very good, thanks for the info!

[Robert A. Zeichner]

Dick is a good friend of mine and I made some GG's using his method before his article was even published. I used the 3 and 5 micron al oxide from W-B as well. What I used for a grinding tool was a 2x2 tiffen diffusion filter I had laying around. Absolutely no use for this as a filter so it became my grinder. I then needed a way to easily hold it and decided a golf ball would feel nice to grab. So then I decided to have some fun at the local hardware store. I asked this 80+ year old guy who worked there forever, if he had some kind of adhesive that would glue a golf ball to glass! I kind of knew what he was going to recommend as I had seen the display in that store for decades! He escorted me to the PC7 display and said here, this should work. The display was a glass bottle with a golf ball glued to it. I just wanted to put a smile on this guy's face. How many times does someone come in to a hardware store wanting to glue a golf ball to glass?

[jon.oman]

Good information here. Now, I can do my own!

[gevalia]

Interestingly enough, I also did 2 GG yesterday for my 4x5's. Bought the 3 microns as well but also bought some brown/red 500 micron alum oxide. I started with the 3 micron but soon found that there wasn't enough cutting power to smooth out a few faint waves in the glass. The 500 did the trick quickly - 10 minutes or so. And then I use the 3 micron after that for 40 minutes or so. I just used another piece of 4x5 glass I had laying around as a tool and it worked very well. I bought 8 ounces of each and used so little that I am sure I could do 50 more easily so keep that in mind.

Now for light. Very unscientific mind you. The 1st GG was as a backup for my Chamonix 25n2. It yielded no difference over the original Chamonix GG when using my pentax spot meter. The 2nd GG was as a backup for my Agfa/Ansco (real old glass) and it was around 1 1/3 brighter. Light source was a lamp in pitch black room.

[IanG]

There's a balance where the fineness of a screen is optimal in terms of contrast, brightness and useability. Too fine and you loose contrast and it can be harder to focus in poor light.

I've measured an improvement of over 2 f stops brightness with an original Graflex screen and a new one I made in the spring. I've made well over 30 screens in recent months and all have been significantly better than those they replaced, having said that some I just reground.

For grinding blanks I have some 3"x3" thick glass which i bought from my glass supplier when U began, it's best to have blanks that only get used with one grit. With these thick blanks there's no trouble grinding to the edges at all.

Ian