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View Full Version : Made a ground glass yesterday.....



Joe Forks
9-Dec-2010, 07:39
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
9-Dec-2010, 07:52
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
9-Dec-2010, 08:12
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
9-Dec-2010, 08:50
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
9-Dec-2010, 08:53
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
9-Dec-2010, 09:14
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
9-Dec-2010, 09:16
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
9-Dec-2010, 10:12
Good information here. Now, I can do my own!

gevalia
9-Dec-2010, 10:23
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
9-Dec-2010, 10:47
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

Joe Forks
9-Dec-2010, 12:57
Ian,
I think it was just ME having problems staying in the corners. Looks like two corners could use a little more grinding, but the other two are good to go. I spent 5 hours grinding this glass. I knew a 12x20 would take some time, still I got impatient.

I didn't measure the old screen, but this pops right into focus in the backyard without a dark cloth. For sure it's brighter, but not sure how much.

Here's a couple photos one with a flash and w/o

Nathan Potter
9-Dec-2010, 19:33
A grooved lapping tool will work a bit better than another piece of glass - the idea being that any slightly larger pieces of lapping debris will become trapped in the grooves and not scratch the glass as you grind away. 3 to 5 um grit is fairly fine so will show a brighter and finer image but more of a "hot" spot than the more typical 600 or 320 grit.

I use a grooved stainless steel block for the purpose. Any hard material will do. Mainly you want the grit in water solution to move freely and randomly between the tool and the glass, while the depth of the grind damage is a function of the force you put down on the tool. Hence a heavier tool is easier on the arm.

Nate Potter, Austin TX.

cosmicexplosion
10-Dec-2010, 02:29
can you use a buffer and grinding paste like you use for engines?

ia there an electric option?

Jack Dahlgren
10-Dec-2010, 12:50
can you use a buffer and grinding paste like you use for engines?

ia there an electric option?

I just gave it a try with a random orbital sander.

In 30 seconds or so 60 grit gives a reasonable opacity.
100 grit polishes too much and results in being able to clearly see the lens opening rather than just the projected image.

The problem is that it is not truly random so there is an underlying swirl pattern that is visible. At least that was the case with my short experiment.

If I were going to do it I might use 100 grit with electric assist for the first step and then finish by hand.

Daniel_Buck
10-Dec-2010, 13:14
just curious, I wonder if glass etching compound would work and provide a decent view?

Jack Dahlgren
10-Dec-2010, 13:59
just curious, I wonder if glass etching compound would work and provide a decent view?

It might, but you don't want to etch very deep. It is easy to try...

IanG
10-Dec-2010, 14:04
I just gave it a try with a random orbital sander.

In 30 seconds or so 60 grit gives a reasonable opacity.
100 grit polishes too much and results in being able to clearly see the lens opening rather than just the projected image.

The problem is that it is not truly random so there is an underlying swirl pattern that is visible. At least that was the case with my short experiment.

If I were going to do it I might use 100 grit with electric assist for the first step and then finish by hand.

Using a power tool is over kill and not random enbough, it's so easy to grind a 10x8 screen by hand, it takes me about 10 minutes maximum.

You need #400 grit or finer. I'll be back to the grinding next week :D

Ian

GPS
10-Dec-2010, 14:20
Using a power tool is over kill and not random enbough, it's so easy to grind a 10x8 screen by hand, it takes me about 10 minutes maximum.

...
Ian

First you say building bellows is easy, now you say even grinding one's own gg is easy - if you say tomorrow that building your own camera is easy I think I will stop reading that...;)

IanG
10-Dec-2010, 15:17
First you say building bellows is easy, now you say even grinding one's own gg is easy - if you say tomorrow that building your own camera is easy I think I will stop reading that...;)

Well as I restore cameras and learnt from scratch what can I say :D

Actually I think I'd find building a camera rather challenging but I could get the wood work done very economically. I've had replacement parts made, like a new front standard for the Quarter plate camera in the Bellows thread. A good cabinet maker could make all the parts very quickly.

So no plans to make new cameras :) I find the late 19th C British field cameras are good enough, I'll make a new 5x4 back and a 6x17 back for my Half plate camera in the same way as I made a conversion plate to allow the use of a 120 Graflex RH10 back on my Quarter plate camera.

Back to screens though, grinding your own is so simple and you can easily match the best available, I was a little sceptical and initially planned to buy a few screens from Belgium (GVB) I already had a Steve Hopf screen. However I needed about a dozen screens so potential costs began mounting, so I decided to have a go. A dozen screens 9x12 cm up to 10x8 cost me a less than 20 ($31(

Because I was making a number of screens I was able to grind and compare using different grits and degrees of grinding. Often a double grind with #400 then #600 grit gives a good all-round screen.

Glass & grits are very cheap so it's easy to experiment and see what suits you best. In my case my screens have given many pre-WWII cameras a new lease of life, and my Graflex's (pre & post WWII) are now so much easier to focus.

Ian

Nathan Potter
10-Dec-2010, 17:06
Ian, the 360 to 600 grit range is what I have found most useful - same as your experience. Never tried multiple grinds with different grits on the same plate; that would be interesting - yielding a mix of fracture densities.

Daniel, what is in the glass etching compound that would etch glass? The classic etchant is HF, hydrofluoric acid, very nasty stuff. Using the vapor to etch the glass will yield a frosted appearance on the surface but it scatters the light poorly so yields a very hot center spot in viewing - my experience from actually trying it in a proper fume hood. I think direct wet etching of the surface with HF solution may be used for anti newton fabrication where there is virtually no scatter centers formed but just broad area etching to reduce the intensity of the interference.

Maybe some one here knows the details of the anti newton glass process.

Nate Potter, Austin TX.

Daniel_Buck
10-Dec-2010, 18:41
Daniel, what is in the glass etching compound that would etch glass? The classic etchant is HF, hydrofluoric acid, very nasty stuff. Using the vapor to etch the glass will yield a frosted appearance on the surface but it scatters the light poorly so yields a very hot center spot in viewing - my experience from actually trying it in a proper fume hood. I think direct wet etching of the surface with HF solution may be used for anti newton fabrication where there is virtually no scatter centers formed but just broad area etching to reduce the intensity of the interference.

Maybe some one here knows the details of the anti newton glass process.

Nate Potter, Austin TX.

Nate, I have done glass etching in the passed, but not for the purposes of a viewing ground glass for cameras. The process is very simple and easy, I was just wondering if anyone's tried etching a whole sheet for the purpose of using it on a view camera. Maybe it doesn't work :-)

Jim Michael
10-Dec-2010, 19:07
Dick Blick sells a product called Armour Etch (http://www.dickblick.com/products/armour-etch/).

Daniel Stone
10-Dec-2010, 20:56
the "armour etch" product works well, but on smaller areas(like wine glasses). I purchased some from my local craft shop(Michael's), but due to having chunks of crystal in a soupy slurry, it was harder to apply, even to a 5x7" test screen I was making.

however, finding the glass cheap enough was easy: get the picture-frame glass in pre-cut sizes: 5x7,8x10 or 11x14. Pretty much exactly sized dimensionally, and darn cheap too when you use the 40/50% off coupons they have during sales(just print out multiple copies, and make multiple purchases ;))

rounds out to about $2-3 for each piece of glass, that's 1/3 the cost of getting it from my local glazier's shop, even with a discount :o!

-Dan

JOSEPH ANDERSON
11-Dec-2010, 19:01
Years Ago, A Photographer I Knew Used Fine Pumice Powder To Ground His
Glass. I Don't Think You Could Find Pumice In Powder Form Now. Has Anyone
Heard Of Using Pumice?
Joe A

Randy
13-Dec-2010, 19:16
just curious, I wonder if glass etching compound would work and provide a decent view?

I was wondering that very thing. I had watched an arts & craft show several years ago and they were using the compound to decorate some glass panals, and I wondered if the compound would work for making groundglass.

IanG
14-Dec-2010, 03:20
If you realised just how easy and the extremely high quality obtained by grinding your own screen you'd kick yourself for even thinking of using an etch process.

As soon as I've photographed the Half plate camera I bought 19 days ago I'll be making it a new screen. The glass is in place but someone tried to scratch a new screen, probably using sand paper or similar, but Ill grind that away and it'll be as new in less than 20 minutes.

Ian