Simple but yet important question...
Where the hell can i find an exposure calculator?
This thing is so important and yet i can find one in any shop around. I don't want to order it from the US unless no other options.
Do you guys have one? Where did you get it from? Your supplier?
I got a home made exposure unit with 5 x UV tube and although when i expose it for 5/6min the emulsoin comes off easily (with the hose jet) it is still very slimy at the back and the emulsion then run down my design and very often affect the print...
So i'm guessing i'm doing something wrong.
There's no way i can use the Karcher, it's too powerful and smash the emulsion... (note i don't have the thing to adjust the jet on the karcher so it's full blast)
Hi,
Print your own. It's easy, print 12,11,10.........1 on your transparancy. Place a piece of card between your screen and exposure unit and pull the card through every minute, if this makes sense.
After you have completed your test, wash your screen out and the correct time is the one which washes out reletively easily.
Easier to do than to describe If this makes no sense at all give me another chance to explain
Phil
__________________
I don't suffer with insanity...I love every minute of it!
I obtained an exposure calculator from GK marketing in Lichfield Staffordshire.
What sort of tubes are you using? There is only one good UV tube with the correct spectrum for exposing emulsion, if you do not have the correct wavelength being emmitted from the lamp you will never cure the emulsion. It sounds like you are seriously under exposing the screen.
Well, i think my UV tube are ok...?
They definitely cure my screen in 5min but it is still slimy at the back.
Although it is, when they're dried I can easily do hundred of prints with them.
Which tube do you use?
How long do you expose for with your setup?
If it is still slimy on the back the emulsion has only cured on one side of the screen not all the way through the coating. How long you expose your screens for will depend on the quality and density of your acetate films and the strength of your exposure equipment. I do not use these machines in house but build industrial screen print machines. The problems you have are typical of home made or low quality exposure systems, insufficient U.V. being emmitted from your lamps or the wrong wavelength
being emmitted from the lamps to effect a proper cure of the emulsion. When you have washed off the excess emulsion off the screen and dried if off ready for printing put it
upside down on your machine and expose it again this will help harden the remaining emulsion and help stop the stencil breaking down prematurely.
Thanks a lot for the advices.
What do you mean by lamp wavelenght? Does UV Fluorescent tube have a wavelenght?
I guess i'll have to expose longer to get thru the layers for thicker screen.
My emulsion rarely breackdown but again i'm not producing massively... 30/40 t-shirts at the time.
All lamps emit light through varying degrees of the light spectrum, the optimum tube to use needs to emit UV light at the same wavelength as the emulsion being cured to effect a proper cure. If you are not using the right wavelength you can expose the screens all day long and still end up with poor stencils.
The tubes you need are 2' 40watt 05 Blacklight tubes, the best light source to get is a metal halide exposure unit fitted with a light integrator to get perfect repeatable exposures. The other thing to be careful of is how well you coat your screens, the thickness of the coating on your screens will make a big difference to your exposures on home made kit, if the coating is too thick you may need to increase your exposure time depending on the strength of your system. You should also be aware the UV light being emitted from these type of lamps is very harmful to the skin and eyes and the unit you make should be light tight. I have a supplier for the lamps if you need one.
Brilliant, that's what i call a good response!
Well the tube i have are exactly these ones. This is why i want an exposure calculator in the first place. That would help me out right?
I know its all about exposing the screen the right amount of time and until now i just let me screens for 5/6min...
Anyway, i'll try to get one of these exp calculator and do some test...
Thanks
When you wash your screens put them in a tray with warm water and let them stand for a couple of minutes then wash them out with a shower head attachment using warm water, you should find the unexposed areas of the screen wash out very easily
( if you have exposed the screen correctly). A simple exposure calculator can be made
using a small acetate film dividing your screen up into 8 sections, (ensure your acetate film is totally black and does not let light pass) black out 7 areas of the screen and then expose the first exposure to say 4mins, then black out your first exposure and expose the second section to 4mins 30sec, carry on until you have exposed all 8 sections of the screen, at 30 second intervals, make a note of the time on each exposure and washout the screen you will eventually reach an exposure time to suit
you.
Souffer makes a greyscale not an exposure calculator. You can get one in England from www.sericol.com out of Broadstairs. probably also from Saati and from Sefar in Switzerland and Italy
Where to find an Exposure calculator?.... 
If this makes no sense at all give me another chance to explain
