Halogen Lamp bulbs/ exposure time adjustments advice needed

Post your questions, suggestions, ideas and advice to issues you have run into in your screen printing shop.

Moderator: Moderator Team

Post Reply
messenjar
Just Browsing
Just Browsing
Posts: 14
Joined: Tue Jul 18, 2006 12:47 pm
Location: UK

Halogen Lamp bulbs/ exposure time adjustments advice needed

Post by messenjar »

Hey every one, I finally got stuff sorted got images printed directly onto acetate and other bits and pieces.

But when I went to test my lamps one wasn’t working thank God I hadn’t coated the screens first. so I thought it would be straight forward to get a replacement bulb boy was I wrong I tried local hardware stores and the internet but cant find any 250w ones thats will fit in my lamps, I can only find 300w, 500w and 200w ones

My current set up was 2x 250w lamps so thanks 500w for 9.30mins so I was thinking that as I can't seem to find any 250w replacements that I could buy 2x 300w ones as my local hardware store sells them and adjust the exposure time but I don’t know how to do this or should I get 2x 500w and half the expose time is it that’s simple

Any advice and suggestions are welcome need to get this issues resolved as soon as possible as it’s stopping me doing anything.

Blessings rema
User avatar
d fleming
Moderator
Moderator
Posts: 546
Joined: Mon Apr 03, 2006 3:33 pm

Post by d fleming »

Run a step wedge test. Place screen in exposure unit. Cover 3/4 more or less of art with a piece of cardboard to block light from screen. As exposure continues, move the cardboard to expose more of the design marking the screen with a grease pencil as you go so you know the exposure times of various areas. You could even pre-mark the screen so you can easily and quicly move the cardboard to each succesive area. When you get a section that is acceptable at washout, there is your exposure time. It'll cost you a little time and 1 or two coated screens, but is the easiest way to figure out the exposure time for your given situation and setup. There should be a sheet given from manufacturer of emulsion giving you exposure and coating suggestions. At least there is with Ulano. I keep one nailed to the wall of the darkroom for everyone to reference. Good luck
messenjar
Just Browsing
Just Browsing
Posts: 14
Joined: Tue Jul 18, 2006 12:47 pm
Location: UK

Post by messenjar »

thanks for the suggestion mate
jklaflin
Intern
Intern
Posts: 20
Joined: Wed Sep 13, 2006 2:03 pm
Location: Montana
Contact:

Post by jklaflin »

Another method is as follows...

One thing I have done is a home-made exposure "calculator."
Cut a piece of thick, opaque (can't see through it) paper into 1 inch strips.
Put your artwork on a screen and then cover most of it with the paper strips - put the strips as close together as possible. Start exposing your screen and set a timer for every 30 seconds (or 45 seconds, or 1 minute - whatever you want). After 30 seconds, turn your exposure unit off, remove one of the paper strips, and then replace the screen to the exposure unit. Repeat this process as many times as you wish. Just remember to keep track of the time. Remember - the image under the first strip you remove will have the most exposure time - the image under the last strip will have the least exposure time.
After removing all the strips you can still expose the screen if you think it needs a few more minutes. For instance... If you use 10 strips of paper, removing one every 30 seconds, it will take 5 minutes to expose. If you know that it takes at least 7 minutes to expose the screen, expose the entire screen for 4 more minutes. Then your intervals will be 4:30, 5:00, 5:30, 6:00, 6:30, 7:00, 7:30, 8:00, 8:30, 9:00.
After you have used all your paper strips, washout your screen. You will be able to see the progress of the emulsion setting up and be able to determine what the right time period is for exposing your screen.

If you want, you can get even more specific in finding the time. If you determine that the emulsion is set up best at 7:00, you can do the test again, removing a strip every 3 seconds, then exposing the screen for another 6:45. Then your intervals will be every 3 seconds from 6:45 to 7:15. You can get very precise using this method, but I myself have never found it necessary to do more than 1 test.

Hope this helps. I know it's extra work, but it only uses up 1 screen, so it's not too bad!
messenjar
Just Browsing
Just Browsing
Posts: 14
Joined: Tue Jul 18, 2006 12:47 pm
Location: UK

Post by messenjar »

So sorry everyone seems like i have been mistaken all this time my bulbs are actually 500w each and not 250w so i can just go get another set from my local hardware store sorry for wasting you guys time.
User avatar
ROADSIDE
Administrator
Administrator
Posts: 458
Joined: Fri Feb 24, 2006 4:36 pm
Location: South Jersey
Contact:

Post by ROADSIDE »

only takes me 125 Light Units to expose my screens.....

NUARC!
.... I can give you my opinion but I can't tell you if it's right or not.
messenjar
Just Browsing
Just Browsing
Posts: 14
Joined: Tue Jul 18, 2006 12:47 pm
Location: UK

Post by messenjar »

oh ok i'm using a diy set up with halogen lamps
Post Reply