[juan427]

My Exposure unit died. I'm trying to get by with placing a 500 watt halogen work light (with the glass cover removed) inside the unit and exposing a 110 screen with QTX for 28 minutes. I placed a heavy board on the screen to hold it sdown. The screen washed out fine except for the fine lines in the times roman font.

Is this caused by:
exposure time too long
exposure time too short
light under cutting the screen
light too far away from screen (it's 24" away)
Or other reasons

 

[ole Jobe]

I use a 500 watt halogen all the time. I use Saati Textil PV and expose from 4-6 minutes depending on mesh. I can hold a 10% dot at 35 lpi. I have a piece of 4" sponge, place screen on sponge, film on screen, glass on film, a 10 lb. weight on each end of glass. Maybe not as good as a vacuum unit, but a lot cheaper.
I'm not familiar with your emulsion, but the time seems too long.
I doubt if you are getting good contact with your set-up.
Either of these could cause loss of detail.
God Bless.

 

[wonubee]

I use a 500 watt halogen at 16 inches away I put a piece of glass on top of the film on the screen. I use QTX emulsion and I expose for 8 to 10 minutes depending on number of coats of emulsion for a 110 and 156 mesh and I got 12.5 minutes for 230 yellow mesh coated 1/1. I get great half tones up to 55 lpi and no washout problems. Hope this helps.

 

[in2infinity]

Loss of fine detail typically indicates overexposure and/or undercutting. Given your length of exposure I would put more money on the former.

Do yourself a favor and get an exposure ramp. At most you'll pay $20.00 for it, and some vendors will throw them in free when you order emulsion, screens or other exposure supplies. Even if you pay for it, it'll save you an incredible amount of time, frustration and significantly reduce your wasted materials ... in other words .. it'll more then pay for itself.

 

[bootlegclothing]

i use a 500wt halogen at the moment as well (working on a better set up) but I do it at 16" off the screen and about 15 mins does the trick for me. if it has high detail I may leave it on for a min or two extra but 15 seems to work for me.... I was told to experiment until u find out what works for you....

I plan on making another exposure unit with either 2 500 wt halogens or maybe something else (black lights reg flor tube lights etc) just not sure what to switch to so if anyone has ideas for me as well that would be great.... I could make a new post but didnt want to clutter up the site if we could kill 2 birds with one stone..... hope I didnt goof doing this if so sorry in advance

 

[PositiveDave]

My guess is that it's light undercutting.
http://www.t-shirtforums.com/t-shirt-articles/t108270.html

 

[BroJames]

The TS indicated he has exposure experience and is temporarily using a 500w point source 24" off artwork so undercutting is less likely. 28 minutes seems a little long for whatever emulsion so underexposure is a little unlikely.

What is the UV source of your original exposure unit? Could the times roman font, or its pointed edges, be too fine for the 110 mesh? Can you post a picture?

 

[bootlegclothing]

oh ya are you putting something on the underside of the screen??? black cloth black poster board etc etc...... something. but ya 28 seemed like awhile to me as well I thought my 15 mins was long