Discuss the different types of equipment needed for screen printing. Topics include manual screen printing presses, automatic presses, dryers, folding machines, starter kits and high end machines.
I'm in the process of refurbishing a Douthitt DML vacuum frame that was in pretty rough shape. I've run all new air lines and tubing and it's starting to look really nice again, the only thing is that the glass is quite deeply scratched in a lot of places. So, my first question would be whether or not the scractches will affect my screen burning. I'm assuming that they will since a little bit of dust can cause some big problems. My second question is, what sort of glass do I need to replace this with? Just a standard plate glass? I'm hoping I don't need some expensive special glass. Okay, and for my final question, does anyone have any ideas on how to protect from scratching the new glass after I replace it? This is a pretty large frame, for large screens, so I can see how in normal use it would be very easy to scratch the glass with a 50 pound frame. I couldn't put any kind of padding on the corners, because that would kill the contact between the mesh and the film. Any ideas? Just be very very careful? Thanks!
We use 1/4 in. plate glass. Just be sure of the size, call the local glass company and they will cut it to size bring it out, place it on your table. You don't need or want any padding as the glass needs to be flat all the way around. The scratches are caused by being careless when putting the frames on table also some ink will end up one the glass over time from residue on frames. We use a razor scraper to remove this but be sure not to scrap it dry, spray with glass cleaner then scrape. Good Luck, John
The last time I made an exposure unit I sprung for special low-iron glass and frankly, I can't say that it improved my exposure times, although I expected it to.
Regarding plexiglas, I've heard that it can contain UV inhibitors.
And regarding scratches on the glass, you could just slip a small square of pellon paper under each corner of the frame to help prevent scratches. That wouldn't affect mesh to glass contact. Also, I just bought an AmerGraph exposure unit, and I always put a small square of dense foam rubber cut from some cheap floor mats on top of each corner to (hopefully) extend the life of the blanket.
Yeah, I basically went for the 'it's just glass' premise in ordering my replacement glass. I didn't ask for seed or inclusion free, so I hope that's not a problem. I kinda screwed up though, because I needed 3/8" glass and I got 1/4", but I should be able to shim it. The guy that I'm buying the glass from will rent suction cups for installation, do you guys think that would be necessary? I'd imagine we could lift it by hand and just clean the smudges after it's installed, since we took the old glass out by hand.
The guy that I'm buying the glass from will rent suction cups for installation, do you guys think that would be necessary?
I've never changed a large sheet of glass myself, so take anything I have to say with a grain of salt.
How large a sheet are we talking? I have a small one I might do without cups, but I've used larger ones I wouldn't dream of trying without (like three feet vs. seven feet). Having pulled the glass out yourself, obviously you've already got a pretty good idea. In will be harder than out though.
On the other hand, this isn't like putting glass in a window: whereas that usually involves holding it vertical and sealing it in, in this case you can presumably move your exposure unit around to whatever position makes it easier on you.
Some things I'd consider:
How much are the cups vs. the replacement cost of the glass if you drop it?
Do you have health insurance, and are you adverse to plastic surgery due to lacerations?
The reason I suggested call a glass company is this is not house window glass. Its heavy and has to be transported correctly. They come out and place it on your table + Take the old glass away. They use suction cups to set it in place, if they break it they replace it. The reason to use 1/4 in instead of 3/8 is its more cost effective as most store fronts use 1/4 inch. Tempered glass can not be cut and is used for store doors because it has a higher tinsel break point. (so little johnny running into it dos'nt get cut) Tempered glass is plate glass that has been cut to size and (stressed) baked. When transporting glass it needs to be on a flat surface or on blocks at both ends if vertical. Like Solmu said its a kind of insurance.
Good Luck, John
Have to agree with Uncle John it is just glass. . . matter of fact I have plexiglass in my exposure table that I picked up from Lowe's
Acrylic plastic (like Altuglas International's Plexiglas®) only transmits 9% to 69% of UV energy, compared to 78% to 93% through glass in the 400 nanometer to 350 nanometer UV light range.
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How are you measuring? retired Ulano Technical Support Screen printing since 1979 - SGIA Academy Member
Exposure Unit Glass 
Re: Exposure Unit Glass 
