Homemade exposure unit.

For the best explanation I’ve seen, take a look at:

http://www.silverclayart.com/ppplates-instr.htm

Don,

You should definitely check out the link that Stefan posted.

Those screenprinting exposure unit plans are not unique; they’re floating around on the internet in several places for free. Plates hold a higher degree of detail than screens, meaning that it’s easier for them to hold mistakes as well!

Screenprinters have a lot more leeway in their ability to goof around with exposure. A gallon of direct emulsion for printing is around $50 and will coat hundreds of screens. How many plates will you have to order and burn in order to fine tune your exposure?

If you’ve got to make one, you need a 21 step grey scale to judge exposure and a source of UV light preferably around 360nm. Find a plate supplier and stick with those plates and the recommendations, or be prepared to conduct multiple exposure tests.

The lamp I got pumps out UVc at 280 nm. Will it work?

Depends on the plate; best to check with the manufacturer first. They won’t bite!

The idea on the quality of the UV is balance between exposure speed and strength of exposure. Plates that are made outside of the recommendation sometimes experience failures. In a pinch, you’re probably fine with a step scale test. But it may be more cost effective to get the recommended lamp in the long run… all this depends on if you’re in a production environment or a hobby one.

Hi Don -

I built an exposure unit with off-the-shelf ballasts and bulbs from Home Depot. I used 4 18-inch “daylight” fluorescent bulbs spaced about 1.75” apart, housed in a box/stand with a shelf about 2.5 inches below, sort of like a mini tanning bed for the plates.

In my exposure testing (using KF152 from Boxcar), I used the Stauffer gauge to get a ballpark for my exposure.

I use “negatives” from Kinko’s - just their transparencies that are printed from files I give them. I sandwich two (carelfully registered) transparencies together on the photopolymer, under a sheet of glass (non-UV of course), held with alligator clips all around. This is much like the metal-clay artist whose link was mentioned.

Are these professional quality? No. But I can hold 1.5 pt. lines pretty consistently, and type over 10 pt is fine.

I should mention the exposure time: 50 minutes! I’m still experimenting with this unit and I’m sure to discover some refinements along the way.

Good luck to you - I’m sure you can get something going if you’re handy, patient, and methodical.

I originally also made plates on the cheap by getting 18” flourescent light fixtures and placed two black lights in them.

This is where i learnt how to do it:
http://www.wholelottawhimsy.com/wo/content/learn/video/PhotopolymerPlate

I got the supplies from their shop too :)

Give it a try.

Forgot to mention - i got the photopolymer from a commercial shop that let me take some undeveloped samples cuz i was an arts student :)

For polymer exposure—Do I need to invert my line art? i.e. black to white and vice versa.
I figure, since unexposed will wash out, we need white of my the drawing to print black on film, right?

I’m not familiar with the process of exposing polymer plates, but if it is anything like offset plates a lot of commercial printers are getting rid of their plate burners for computer to plate imagers. You might want to check with some commercial shops. We tossed our plate burner in the recycling a year ago.

You are correct. What are you using for film?

Daniel Morris
The Arm Letterpress
Brooklyn, NY

Steve - use BLACK UV bulbs in your ballasts.. it creates plates in seconds.. about 45 to be exact.

Before we got our commerical unit at the museum we used a set up that was built from information that one of the techs gave from the plate material supplier.
We made a home made vacuum frame and used suggested lamps F20T8/BL they give the light level 365nm.
Set exposure to solid 15 on your scale
Lamps should be set 4 - 5 mm and 2 to 2.25 inchs from the surface.
If the lamps are to far away intensity problems, ie weak shoulders on the surface edges.
If lamps are to close there will be a barring effect showing.

We made made a wood enclosed box with a plexiglass top and cut grooves with a dremel tool then drilled holes and had access to an old slurrpy machine vacuum pump set a sheet of kreen across the top and it worked. A rectangular tub was made from sheet metal and mounted the ballests and tubes at the set heights. mounded upside down ontop of the wood base with a piano hinge.

Exposure times were with in 10 seconds of the commercial unit we finally became owners of.

Hope the information helps.

John Hunt
Mackenzie Printery and Newspaper Museum

I stitched one together out of junk. Old enlarger column and a UV light (from art etching suppliers), a vacuum lid off a junked platemaker (offset) a sheet of plate glass to size, and an old vacuum pump off an Eskafot process camera. Its been going ten years. I process in a photo tray and sink washing at around 20 degress cel. and using a good goats hair broad brush. Dry by hairdryer set to warm ,post expse. Done! Be careful to wear eye protection around UV light.

I try to get my letterpress printing done with cheapest possible route and I have also built my own exposure unit. I used scrap wood (free) to build a box and laid a $7 sheet of glass over it. The box is 25” x 25” and a 24” sheet of glass lays inside (about 3 inches away from the bulbs) with one of the side walls hinged so I can get to the bulbs inside. I bought two fluorescent light fixtures from Lowes and each one holds two 24” unfiltered UV black lights found at a specialty light bulb store in town. I am sure there is a light store around you somewhere. So all in all I am about 40 bucks into my unit and works great! For the polymer plates I get from boxcar I throw the plate with my film negative on top of it in a Space Saver bag I got from wal-mart for $5 and vacuum seal it shut and that gets me a really nice seal. And the bag I can use over and over again. I accidentally punched it a hole in it and all I had to do was throw a piece of duct tape on it and it works fine.

After the exposure I wash it out for 5 minutes in 68 degree water with the nylon brush I got from boxcar (works great) and dry it off and it’s ready to go. I usually post-expose it for 20 to 30 minutes to make sure it’s nice and hard, but that could be done by putting it outside in the sun to for a while.

My method is not professional by any means but it works great and it was super cheap. Hope this helps!

I made an exposure unit myself—I had read a method in Dan Weldon’s book but at one point he said hire an electrician and I lost interest. Then I found some smaller fluorescent fixtures at Home Depot that can be plugged into each other in a line like you might use for under cabinet lighting. It was easy to attach them to the inside top of my wooden box and plug then in a series. I discovered that the wooden box is too heavy to easily lift and place over my plates so I just cut a door with hinges in one side. I expose for about 3 minutes and I ended up putting my plates on top of a box to raise it closer to the bulbs. I’m really happy with the results I’m getting! I have about 10 bulbs—I started with 8 but had more room so added two more. If I were doing it again I would make it like a light table and put my plate material on top of a glass platform. I saw a tip to use a space bag to create a vacuum to keep the plate and negative together and that works pretty well but the darn space bag people wrote stuff all over the bag so I have to carefully place my plate to avoid problems. I’m teaching a class next week and so I decided to try sun exposure and it’s working pretty well with the 94FL plate from Boxcar. I notice the shoulders aren’t as good as the UV exposure plates. I’m wondering if the Kreene might help with that?

I forgot to say I found black light bulbs for the small units online after some searching.

try a piece of foam rubber, put a sheet of bond paper over the foam, then the plate with the negative on top, then a piece of glass should compress the foam a tad and give a good contact of the plate to negative.

Dickg, I’ve had that same thought for when I build my plate-maker. I figure I can try it and if it doesn’t work I can always retrofit the plate holder as a vacuum table. Has anyone ever actually tried using foam backing and glass? If so, did it produce acceptable plates or should I just go ahead and make it a vacuum table from the beginning? Thanks!

Michael Hurley
Titivilus Press

I find this discussion amazing because photopolymer plate processing costs have not risen significantly since the early 1990s, though raw photopolymer plate costs have. Making your own actually costs more.

Same with film negatives. Processing has dropped roughly 40% even though silver has risen in costs something like 4x.

This is like the best deal in the world.

The prevailing industry provides purposeful deflation, at amazing quality, and yet, as the fellow proclaimed “My method is not professional by any means but it works great and it was super cheap.” Not by a long shot.

Gerald

i think a vaccuum would work the best, but i have used the foam for a long time with ok results. i don’t make very many polymer plates, maybe one or two every 3 or 4 months.

I use a nuarc flip top platemaker for the vacuum and made my own black light array out of standard black lights from Walmart set as close as I could get them together. I have a timer set on the unit to automatically turn the lights off at either 3 minutes exactly or 2:40 sec depending on if it is all art or has text. I have had consistent exposures with this set up for years.

Here is what the exposure box looks like.
http://www.flickr.com/photos/its_fancy_letterpress_studio/3786854329/in/...

Don’t know if you care to watch it or not but 4 years ago I made a video of my process. It is dry but it will give you the idea. It is not the full process I use but 95%. It took a few weeks of trial and error to get my exposure times down and the washout process up to speed.
http://www.youtube.com/watch?v=JeaLq-71hk4&list=UUXFHFZWrfu2rBhEaUSCc72g...

The exposure box sets about 3” off of the art on the vacuum table. Then you have to hand wash them out, air dry and reexpose to harden them a bit more.

My system saved me a considerable amount of money over having someone output plates for me. The hard part is the hand washout. And there are limitations. I do not create plates over 5” x 7” because it is very hard to wash them out in time. If you take too long you plate turns to goo.

So you have to decide if the extra labor is worth the cost? Are you crafty enough to do it on your own? If the answer is no then buy a plate making unit or pay someone to do it for you.

I stopped making my own polymer plates a year ago because I do not have a water supply in my shop where my equipment is. Right now it is more convenient to order them and adjust the cost into the project. If I had running water and the equipment set up I would probably go back to my home made set up until I set aside enough money to buy a platemaker, cause hand washing a plate sucks.

I don’t quite get the saving money thing. Even ignoring the costs of building an alternate set up, just the raw plate stock used up in the experimentation to get it right has to be figured in here right? Right? And no one here seems to be claiming they are making plates that are good enough for resale to a client? I make plates for resale and buy the raw stock in bulk (which is a lot better pricing than buying it short). When I occasionally blow a plate that hurts. And even with state of the art setups you are going to mess up.

I don’t get this. This isn’t printing, making plates is not creative, they ultimately have to render the image exactingly, just like any other imaging technique. I’m assuming the same situation exists for those making their own negatives. Toner, film stock costs, experimentation, and still not quite up to par.

I have yet to encounter anyone who discovers a better technique or tool who reverts backward.

Gerald
http://BielerPress.blogspot.com

I have made over 200 plates with my set up, and while the first 15-20 may have been sketchy, the ones after that were very usable and I was able to get all the polymer washed out in time down to the plastic.

To preface this. I wrote down in a sketch book every exposure and washout time until I got a solid plate! If you are not willing to figure out what works with your set up then just buy finished plates from someone with a proven track record like Gerald or Boxcar.

This is how the savings works out for me. I usually went with a KF 152 which would cost .65 a square inch.
So if I has art that would require a 12” x 18” total area it would cost $140 + 10 shipping. So 150 total

For me to do it it would cost closer to .34 a square inch.
Unexposed polymer $53
Adhesive backing $2
Negative from film output house $20

I was lucky putting together my set up. I only have $180 into the vacuum and exposure unit. If you are putting more into your set up, save for a professional platemaking unit or farm it out.