Trials & tribulations of home made exposure unit

[MearlH]

SO, JUST BUILT HUGE 26 X 40 EXPOSURE UNIT. First try was underdeveloped, which worries me. I have 4 t8 36" 30watt cool white bulbs evenly spaced. I am hoping that i just need to expose longer. First run was only 25 minutes. Or am i using the wrong bulbs. Maybe higher wattage bulbs would be a better way to go. I here people talking about black light bulbs working well. Any advice would be great. Maybe 30watt 36" t8 blacklight bulbs (any one know where to get these)? Just got my new screens from ryonet and love them nice and big. below are a few photos of the monster i created (hopefully i can get it dialed in and start printing) Also a pic of my latest project idea

[MearlH]

I am an idiot and find it near imposible to post a fucking picture on this website. I have photos on snapfish (online photo album) how the fuck do i get them to upload on this site. I love red x's and may consider painting one on the side of my light box but that is not what it or my latest project ideas look like. I am not a techie just a old school artist some one help me before i shit myselt.

[BigmanJames]

You are going to have to do a step wedge test or buy an exposure calculator.
25 mins seems a long time . Are you putting your screens directly on the light, what is the distance away? I use a $10 500 watt flood light at 2 ft away. Takes 40 mins but works everytime. A flourescent unit should burn in less that 10 mins from what ive read.

James

[vrooooom]

I am an idiot and find it near imposible to post a fucking picture on this website. I have photos on snapfish (online photo album) how the fuck do i get them to upload on this site. I love red x's and may consider painting one on the side of my light box but that is not what it or my latest project ideas look like. I am not a techie just a old school artist some one help me before i shit myselt.

You're probably using the wrong url? Right click the image and go to "view this image" then snag the url. But, I don't use snapfish. I think I read that they restrict pictures to your contacts on snapfish, so it may not be possible Use a better image host like the ones in the previous thread you posted.

[steve w]

wrong bulbs. get black lights, or, even better, unfiltered black lights.
there are about 50 threads on the subject here

[strawberryluna]

i use 60 watt daylight fluorescents, long assed 48" inches, they come in 36" lengths too. get a housing (or however many sets you can fit) and try those. my burn time is 2 minutes. my homemade unit is something like 40x56, i forget exactly. but way big enough for 2 26x31 screens to expose at the same time.

sounds like you are definitely underexposing and probably using the wrong bulbs.

[MearlH]

thanks everyone, Steve, I think that was my problem, i went onto ryonet and found some ultra violet 36" t8 bulbs for about $15/each I need 4 of them (and a paycheck before i order them) so will probably get those at the end of the week and hopefully it works out better. I think with the cool white bulbs I had in just didnt produce as much uv light. I will try again to post a photo of my contraption for further critique. As far as distance it is a rectangular shallow box shape with a routered inside edge to allow for glass to cover the top and sit flush. I put my screen face down and cover the back with a cardboard scrap about 2 inches or so above the lamps. Would it be better to fill the back with black foam cut to the diameter of the inside of the screen? Also I built the box from wood, do you think i need to paint the inside white to reflect more light or add mirrors inside or something to that effect, or do you think with right bulbs everything will be schnitzeltastic?

[strawberryluna]

eff the expensive bulbs, seriously just go to lowes or home depot and get the daylight bulbs, less than $5 each. BOOM you're all set.

i do think that having a black backing, rather than cardboard is also going to help a TON. you want any light that is going through your screen to stop right there and burn your stencil. i have MDF cut to smaller than my screens' inner dimensions, with foam padding spray glued on, and then that brick is wrapped in black felt and sealed with duct tape, with a cheap cabinet door handle screwed into the back (not screen facing) side in order to have enough compression on the screen to make sure that the film and screen are nice and tight up on each other during the burn. if you are just resting cardboard or blackboard over your screen, you might not get enough compression weight and will definitely have VERY blurry images that don't burn properly.

my exposure unit is raw wood. i meant to paint it white, did some tests, and realized i didn't need to. you might, but it's not always needed if you have enough light. avoid mirrors, that could just bounce light all over and super fuck your burns up.

[MearlH]

cool, thanks for the input. So i think i will look at the daylight bulbs, Like I said the cool whites have a pretty opaque coating on them. so i will check those out. (i am so itching to start printing but always have technique related bullsquat(bullshit's cousin) to deal with) I will also grab some black foam backing to place inside the screen when buring sound like a fly idea. One other question. I typically tape my transcparency to the screen, then place the screen down on the glass exposure unit. Is this kosher? You dont tape your image to the glass of your exposure unit do you? (I was doing pretty well burining small screens in my closet with a pie shop reflector light but wanted to expand my exposing abilities so i do appreciate all your help.)

[strawberryluna]

i do tape one corner of my films down to the glass, and then slide my screen around to find the right spot. it's just easier for me that way and i don't have to worry about pulling the tape off+some emulsion.

and trust me, for as long as you screenprint, little technical issues will plague you. temperature, humidty, new bulbs, new emulsion, whatever. all of the elements of screenprinting are super sensitive. but once you get your time down, you should be in taller cotton.