Mercury Vapour exposure unit:

[Tom]

Originally Posted by steve w

the diagonal of your biggest IMAGE, not screen

Okay, Whats the standard printed poster image size? I print tees at the moment but no harm future proofing the box to allow me to do larger images.

[Tom]

By my calculations a 27x19 poster would need 51" distance from bulb to glass. Too big for my space. So the diagonal of my actual largest image would be 25" x 1.5 = 37.5" distance. Correct? Is it okay to have this as my fixed distance then build the box & work from there?

Apologies about all the questions, I know these exposure threads are annoying but at least Im not using a microwave

[Andymac]

Isn't it A 14 or some goofy system over there?

[Andymac]

That's only because you don't have microwaves in Ireland, isn't it?


Calc sounds right. The further away the longer it takes. If 90% of your screens are small t-shirt size, then that's a lot of time you could be spending drinkiing guiness at the pub

[Tom]

I dunno, I went on Glynn Scrawled page & all his posters are 19" x 27". It might be A1 maybe.

[Tom]

Ive googled & searched on here to no avail. Does anyone have blueprints for a vacuum lid for diy exposure unit? Tips, hints etc.

Thanks.

[Switch]

Hey Tom, see you got the lamp then. Its pretty easy to workout how to make one. Although the rubber sheet will cost you a bomb. I sold a print down frame about a yr ago. Is your unit lights pointing upwards not horizontal like a halide ? If so why do you need a vac.

I use heavy books inside the screen to make the stencil trap as tight to the screen as possible.

[Tom]

Yeah i got a 400w metal halide yesterday. Going to build a box with glass top & vacuum lid. I can get the neoprene blanket here & Im going to use an electric air pump for inflatables (which also deflates, handy) for the vacuum. Im exposing from underneath.

[Switch]

Righty ho. I still wouldnt go with the blanket. I know plenty of people on here and screeners that use books as a method of trapping the screen tight. The glass is the dearest thing you will buy. I have a photo somewhere of mine. I use 2 x 500w lamps at 23" set 6in apart for my exposing of an A2 posi. Timing wise its 15mins, slow but it works fine for us all here.

I guess what andy mentioned before applies, if you want it quicker the distance from the light to the glass is shorter, although you will have to look out for hotspots.

[Tom]

Why is the blanket a bad idea? Because of the cost of glass? Is it tempered glass i need? What thickness would i need if I use a vacuum lid? Sorry for all the questions.

Edit: My girlfriend is a framer, I read in another thread that framers use 1/8" optically clear glass. If its too thin could i use two sheets one on top of the other or would this cause major exposure problems?