# Problems with my homemade Exposure box



## DesignsToSigns (Aug 4, 2007)

OK so I went ahead and built a unit like the one found in Print t Shirts for fun and profit. Now I am having a hard time getting them exposed. What I did was take plywood and made a 24x30 box with two 24" flourescent bulb fixtures inside. I then put natural day light bulbs inside there. Then I have the glass which is then followed by the transparency and the screen. Then I place a cover down. I thought I Read somewhere that I should paint it black so everything is painted black. The book says it should cut my time down to 5 minutes, I tried it at five and no luck, then I tried at 20 and found there was a drop shadow added to the image on the screen. Any ideas am I using the wrong bulbs or something? I look forward to learning something new,

Adam


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## brent (Nov 3, 2006)

Try using 20 to 40 watt blacklight tubes, the ones that actually look like white bulbs. That's what I used. You also might have to play with the positioning or distance between bulbs.
I had a similar homemade unit (I recently got a Hix vacuum lid exposure unit and love it, retiring the homemade box), and used 4 20-watt white blacklight tubes and had a burn time of about 6 minutes.
Are you compressing the screen to the glass? I bought foam board at home depot and cut it to size, used three pieces of it attached to a heavy particle board, then placed that inside the screen with bricks on top. It worked pretty well, but not perfectly. If you're not compressing the screen, the screen may not be pressed perfectly flush against the film against the glass. if you're not doing this and you build a compression lid and try it, I would expect it to solve or at least greatly help your problem.


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## DesignsToSigns (Aug 4, 2007)

Is the black light and unfiltered black light the same?


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## brent (Nov 3, 2006)

I think unfiltered is what you want. There are a few types of blacklight.
This is what I used in my unit 
20W T12 FLUORESCENT BLACKLIGHT MEDIUM BIPIN BASE


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## neato (Mar 21, 2006)

You also need to make sure you're film is TIGHT TIGHT TIGHT against the screen. You need to put some weight on top. I used to use phone books and bricks until I built my own vacuum frame.


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## brent (Nov 3, 2006)

Oh, and if you set up your box, keep in mind the bulbs degrade over time. I used mine for probably six months before realizing that the bulbs had grown weaker and were the source of some screen problems I was having. You'll have to increase burn time after continued use, after a while. To be proper, you should use an exposure calculator film and check it every month or so. My problem was that I was underexposing without realizing it, and very thin and clear layers of emulsion were coating each thread, effectively reducing the size of the holes in the mesh, and were causing serious printing problems until I realized this and increased burn time significantly.


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## DesignsToSigns (Aug 4, 2007)

I did that and they re getting better might need a longer exposure time might have to back tot he old style till I get the bulbs in not sure what I am doing wronf


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## DesignsToSigns (Aug 4, 2007)

Product Information Error Page

Product Information Error Page

*

Which of these three are actually useful in this situation
*


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## SOBER (Aug 6, 2007)

also , did you make sure that the glass is untempered ,no u.v inhibitors........


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## DesignsToSigns (Aug 4, 2007)

Brent just ordered those bulbs thanks for your help and I will let you know how I make out when they come in


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## DesignsToSigns (Aug 4, 2007)

Well the bulbs finally came in and they didnt seem to work any better or any worse. Maybe i need more pressure? How much pressure are you guys putting down on top of the glass? I am not getting what I would like from what i did and I am possibility doing something wrong as many have accomplished this before hand.... So any help is appreciated again!

Thanks


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## UptownGraphics (Dec 17, 2007)

I would suggest making sure that the type of glass doesn't have something that helps block UV rays. I know a lot of glass blocks UV rays and if this is the case, it will be blocking out what you need to get through!


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## DesignsToSigns (Aug 4, 2007)

I am not sure if it does or doesn't it is a piece of replacement glass for a picture frame from Home Depot


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## BroJames (Jul 8, 2008)

astours said:


> OK so I went ahead and built a unit like the one found in Print t Shirts for fun and profit. Now I am having a hard time getting them exposed. What I did was take plywood and made a 24x30 box with two 24" flourescent bulb fixtures inside. I then put natural day light bulbs inside there. Then I have the glass which is then followed by the transparency and the screen. Then I place a cover down. I thought I Read somewhere that I should paint it black so everything is painted black. The book says it should cut my time down to 5 minutes, I tried it at five and no luck, then I tried at 20 and found there was a drop shadow added to the image on the screen. Any ideas am I using the wrong bulbs or something? I look forward to learning something new,
> 
> Adam


If you are using only TWO 24"/20w fluorescent + a natural day light bulb then maybe you need to try increasing it as much as SIX fluorescent (to increase from 40w to 120w). Also check the spacing of the lights which I think should be 4-5 inches apart.


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## InkedApparel (Mar 18, 2009)

astours said:


> OK so I went ahead and built a unit like the one found in Print t Shirts for fun and profit. Now I am having a hard time getting them exposed. What I did was take plywood and made a 24x30 box with two 24" flourescent bulb fixtures inside. I then put natural day light bulbs inside there. Then I have the glass which is then followed by the transparency and the screen. Then I place a cover down. I thought I Read somewhere that I should paint it black so everything is painted black. The book says it should cut my time down to 5 minutes, I tried it at five and no luck, then I tried at 20 and found there was a drop shadow added to the image on the screen. Any ideas am I using the wrong bulbs or something? I look forward to learning something new,
> 
> Adam


I assume if this is a homemade light box..then there is no vacum to hold the film tight to the screen...how thick is the glass? it needs to be at least 1/4 inch so when you put weight on it to hold the film tight to the screen the glass doesnt bow under the weight.if you are getting a shodow effect on your exposed screens ...I would say the glass is bowing..try thicker glass.

I would say 1/4 inch glass would be ideal.

Inked


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## kmapparel (Jul 15, 2008)

astours said:


> I am not sure if it does or doesn't it is a piece of replacement glass for a picture frame from Home Depot


Every piece of picture frame glass that I have run into is made to block most/all UV rays to protect the picture that the glass is covering. I would guarantee that this piece of glass is the source of your problems. You have a decent box, the correct bulbs, and likely sufficient pressure. Now you need new non-uv glass. Find a replacement glass or mirror store in your area. Make sure you tell them you want glass that does not block UV. They'll know what you're talking about.


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## 13Graphics (Jul 20, 2009)

InkedApparel said:


> I assume if this is a homemade light box..then there is no vacum to hold the film tight to the screen...how thick is the glass? it needs to be at least 1/4 inch so when you put weight on it to hold the film tight to the screen the glass doesnt bow under the weight.if you are getting a shodow effect on your exposed screens ...I would say the glass is bowing..try thicker glass.
> 
> I would say 1/4 inch glass would be ideal.



I'll second that. I switched from a piece of 1/8 that worked OK, to a piece of 1/8 tempered the other day because it was a little bigger, and heavier. Man did I regret it. It is warped BIG TIME. I noticed about 4 minutes into a burn, and had to hold it down the rest of the time.

I need to find a piece of 1/4"


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## jimmi (May 16, 2009)

astours said:


> I am not sure if it does or doesn't it is a piece of replacement glass for a picture frame from Home Depot


I am using normal 4 unit of 2 feet florescent light 18W . Set it about 2 inch apart each and distance to screen is about 6 inch. I got the glass from the normal frame making shop. my exposure time is 10 minutes. It just a hobby and the time is good for me now.

Hope it help.
Jimmi


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## iansureprint (Sep 4, 2009)

6mm toughened glass is standard.


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## BroJames (Jul 8, 2008)

jimmi said:


> I am using normal 4 unit of 2 feet florescent light 18W . Set it about 2 inch apart each and distance to screen is about 6 inch. I got the glass from the normal frame making shop. my exposure time is 10 minutes. It just a hobby and the time is good for me now.
> 
> Hope it help.
> Jimmi


I am a little new to this exposure thing but I am not new to silkscreen and have seen a number of exposure boxes in commercial use - all DIYs. These 4 lamps ([email protected]) are quite common with 1/4" glass set 6-12 inches above the light. Some intentionally left the lamp housing unsecured to the exposure box's flooring so they can move it around adjusting the distances between lights, and turning off some lamps, depending on the width of the screen. Exposure time is usually 12-17 minutes with the glass set 12" above the lights.

Just some additional info. Most commercial silkscreeners I've seen doesn't use the scoop to apply the emulsion on #110 screens. They use a prepaid cellphone card (the size of a credit card) to apply the emulsion (mixed with some mineral or distilled water). This is a more laborous undertaking, as it requires numerous strokes, but the coating is purposedly thin. Two tables spoons of emulsion is enough for a 16" x 16" screen (actually 2 tablespoon is more than enough).

Some also used regular bond paper instead of acetate and they are able to print commercial shirts with cartoon images and they are of acceptable quality. I am sure that they can't win over better exposed screens (especially those with double acetate or laser printed) but they are acceptable to customers here. They did apply oil to make the paper less opaque. 

Often, a few books, unopened canned goods, or just anything lying around are placed on top of the screen which often weigh less than a kilogram.

I've seen commercial shirts printed with screens exposed for 12 minutes and less.

However, I've met a commercial printer who did admit that for better details beyond cartoon characters these fluorescent lamps may not be enough.

As to the glass, usually those 1/4" thick glasses bought from local aluminum shops are fine. I heard that 1/8" thick glasses are also fine albiet a little more delicate but have not heard of such glasses warping. Maybe it depends on how well the glass is secured on the box but I really don't know.


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## Alan Buffington (Oct 27, 2010)

Bro James is right, not enough UV light, you need more bulbs. If your lamps can't give you a sunburn they aren't that strong. To show how weak these lamps are it can take 12-15 minutes based on our tests to expose a fast exposing emulsion. By contrast the sun can expose the same emulsion in 30-40 seconds at noon. You need the following to make good screens:

1. Good emulsion, brand name, not some private label stuff. If real hot were you are choose an SBQ pure photopolymer that can be stored at 100 degrees which would kill any emulsion with diazo in it due to diazo dark hardening caused by heat.
2. A decent source of UV light. Switch to the sun in summer, far cheaper.
3. Good film - Must be dense black, if it were sunglasses you couldn't see anything. So if using vellum spray it with lacquer spray (cheap) or toner enhancer and know that you will need to underexpose to get an image. Inkjet, get a RIP that can control ink density and make dense black images.
4. Coat, Store, and image your screens in yellow safe light.
5. Develop indoors out of the sunlight or reflected sunlight, once you go outside you will lock in your image area.
6. If all this fails go to www.murakamiscreen and check out some articles on screen exposure.

Also you can send me an email and I'll send you a drawing of a sun exposure unit. Easily the cheapest DIY exposure unit out there. The sun in summer is one heck of an exposure lamp.

Alan Buffington


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