Make your own plastic groundglass

luisalegria · Expire: 2018-01-18

Anybody who has played around with OLD cameras has probably run into the situation where a new prize plate camera, press camera or folder turns out to be missing its groundglass, or the old one is cracked. Replacement groundglass can cost $15-50 depending on where you look.

Its also common to need to adjust infinity on old folders, etc., for which a groundglass across the film mask is essential.

There are plenty of workarounds for that job, such as clear tape, but its best to have a rigid piece with better visual quality.

Making a glass groundglass yourself is very possible, but its a pain in the bottom and takes longer than one would think. And I don't like the ones I've made. And I can't get the things to ever break neatly.

A few weeks ago I bought a large (2'x4') piece of 1/16" (1.5mm) acrylic from TAP Plastics - http://tapplastics.com/
These sheets come with masking plastic film on both sides.

And a few pieces of Tamiya 800-grit sandpaper. This is used for sanding styrene plastic on model kits.

Cut out a piece of plastic of the right size -the proper size to replace a glass groundglass, or to fit over a cameras film gate - I have made pieces to fit on most 6x9, 6x7, 6x6, 4.5x6 and 35mm.

Cutting is very easy. I use a cutting wheel on my dremel, but a hacksaw with a fairly fine-toothed blade is just fine. Sand the edges until they are smooth, so the piece will lie flat.

Peel off the masking film from one side.

Sand that side with the sandpaper. Best to use a sanding block. It doesn't matter very much what pattern you use. Just sand it until its translucent. It will not take long at all.

Wash the piece.

Peel the film from the other side.

And there you are, a groundglass, better than any glass one, most likely, that you will make in your first few tries. And you can make any size or shape.

TBaker · Joined: 02 Dec 2009 Posts: 344 Location: Canada

Couldn't you use liquid etch on real glass to get the matt look?

Sevo · Expire: 2012-12-03

poilu · Expire: 2019-08-29

great trick, I will try it

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

I have a portable sand blaster rig that I've thought about doing this with before, but now that I think about it, the sand particle size is probably too large. 800 grit or finer sounds like a better solution. I have some clear plastic scrap laying about that I think I'll give it a try with. I also have some rather special sand paper, called Micro Mesh, that was originally designed for use to polish out acrylic aircraft windows that might become abraded after years of flying. It comes in grits from 1500 to 12000. The 1500 grit may be scratchy enough to give the ground glass translucence.

I was thinking about this recently as a way of checking the accuracy of a SLR camera/lens combination's focus compared to what one sees in the viewfinder. But it's nice to know about should I ever run across an old view camera for cheap because its ground glass is busted.

marty · Joined: 09 Apr 2009 Posts: 767 Location: Italy

Thank for sharing, Luis. Sounds like a great idea.

Cheers, M.