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Finally trying my hand at silk-screening, but when I go to wash out the image,all the film comes off. I'm working in the dark (ahem) - image on laser-printed transparency, 110 mesh monofilament screen (cleaned & degreased), wet the screen (lightly), squeegee the film onto screen (via black light), dry overnight with dessicant, screen feels dry when I take it out, put image on glass over big honkin' halogen lamp, put large dark heavy thing over screen over glass, expose for around 18 seconds, wash with warm water & pressure hose.

???

If your film is washing off it sounds like it's not being exposed enough. What film are you using?

Work with the film under a yellow bug light not a "black light".

Ron

Ron's probably right. How long you have to expose the sensitized surface is dependent on three factors: the strength and type of light, the type of sensitizer, and how far the light is from the surface. All three have to be the correct ones for your film for it to work.

Eighteen seconds is a very short exposure time. When I use the sun it takes about 45-60 seconds. Two 40 watt fluorescent lamps about 12 inches above the film take about 7 min.

Ron

I agree with both Ron and Brad, and also want to add you should not wash out this type of film with warm water. Cold water and a high pressure nozzle are necessary.

Avery

Cheryl wrote:Finally trying my hand at silk-screening, but when I go to wash out the image,all the film comes off. I'm working in the dark (ahem) - image on laser-printed transparency, 110 mesh monofilament screen (cleaned & degreased), wet the screen (lightly), squeegee the film onto screen (via black light), dry overnight with dessicant, screen feels dry when I take it out, put image on glass over big honkin' halogen lamp, put large dark heavy thing over screen over glass, expose for around 18 seconds, wash with warm water & pressure hose.

???

Hi Cheryl,

I'm not saying my experience is the right or the wrong way, but here are some tips that worked for me;

Your stencil (artwork) needs to be clean and doubled-up. -That is, solid blacks and print two, trim one off to give you sufficient sapce to sellotape it in place exactly over the bottom copy. Even though the toner in your printer looks solid, this will ensure you get a good solid light blocking black.

Use the lamp that Ron mentioned. At a push, you could make a small light box and cover the front with a piece of Rubylith film. Bright enough to see and work but not to develop your emulsion.

Use a proper coating trough to apply the emulsion to your screen. Coat it front and back. Ulano emulsions are good and they give you a good exposure guide. Different emulsions for different applications/stencil thicknesses. Before applying the emulsion, dry the screen with a hair dryer and after applying the (wet) emulsion to the screen, dry it with the same hair dryer.

The emulsion will deteriorate in time and heat. Keep your mixed emulsion in the fridge.

I started off with two 500 watt halogen yard security lamps. It works but takes ages. You live in a developed country so it shouldn't be too hard for you to get a good light source. It will make all the difference to the quality of your work

Go visit a local screenprinter, they will give you a lot of tips or let you watch them setup. Loads of books at the library, remember when everyone was screening their own T-shirts in the 60's? It's an old trade and that generation aren't shy to help you out.

There's a lot in the message boards at http://www.screenweb.com, similar to the setup with WG. The best book I found was; How to Print T-Shirts for Fun and Profit, you can find it on the bookstore at Screenweb.

When you wash out the screen; do you have a compressor? -fix up a water blaster, same as the syphon sand blasting system people discuss here. Instead of dangling the syphon tube in the water, connect it to a tap and have a steady trickle of water, you don't need a lot in fact less is more. Cold water works okay, it is the blast effect that is the key to removing unexposed emulsion.

Oh, and as I understand it, the emulsion is like a liquid plastic that has a powder of hardeners suspended in it. When the hardeners are exposed to ultra-violet light they change their molecular state and link together to form a matrix that holds the emulsion together and makes a tough material.

Sorry to ramble but I hope some of that will be useful to your quest, good luck and let us know how you get on okay.

Cheryl, I have had good success using Hunt Speedball Photo Emulsion instead of film to prepare silk screens. You need only subdued, normal room light to coat and set up stencil on your screen, no safe light or darkroom setup needed. Exposure for me is 7 to 8 min with no.2 photoflood bulb about 12" above screen in clamp on reflector. I have used old style with bichromate sensitizer, have not tried newer diazo based system yet so I don't know light sensitivity on it. Speedball photo emulsion is available in many large art supply stores or online. The dish sprayer at the kitchen sink works well for most washout with this. Problem areas respond well to a waterpick oral appliance for pinpoint washing out. IMHO emulsion is so much easier and certain than fooling with film.

Best wishes,
Tom in Texas

Tom White wrote: IMHO emulsion is so much easier and certain than fooling with film.

Gosh Tom, I don't agree with you on this. For beginning students, I feel film is the only way to go. Simply wet the screen, cut the film, and press it on. No mess, no having to worry about evenly coating a screen. Ulano makes some of the best films around. Their CDF QT50 film is the most forgiving film I've worked with. Expose it to sun or even when it's overcast and it will develop perfectly. I exposed it during a snow storm in Maryland (for 1 minute) and it sill developed with no problem. It's quick, easy, inexpensive and you get predictable results every time.

Avery

I purchased this film from Tony Glander, my silkscreen instructor, so I don't have original packaging. But it's hot pink if that helps. I will try a longer exposure. I'm using a halogen flood lamp for exposing.

What is the difference between a black light & a bug light? The only goal is not to expose the film, right?

right, except that a black light emits UV rays which WILL expose the film and a bug light is yellow, does not emit any UV rays, and WILL NOT expose the film.

Tony

tony, you scientist-types are always so precise. Do you mean to tell me I went to Spencer Gifts for nothing???

As I recall, you can also actually SEE with a bug light, can't say the same for black light (should've kept those posters...)

Cheryl wrote:tony, you scientist-types are always so precise. Do you mean to tell me I went to Spencer Gifts for nothing???

As I recall, you can also actually SEE with a bug light, can't say the same for black light (should've kept those posters...)

Which is why people use the bug light when they handle the film...

Tony

Cheryl wrote:I purchased this film from Tony Glander, my silkscreen instructor, so I don't have original packaging. But it's hot pink if that helps. I will try a longer exposure. I'm using a halogen flood lamp for exposing.

What is the difference between a black light & a bug light? The only goal is not to expose the film, right?

From the hot pink color it sounds like your film is one of the Ulano CDF QT type capillary films. These films work well under low light conditions for exposure.

Ulano has tech information about this film on their website.

http://www.ulano.com/

This is the film I use and it takes 45-60 seconds in full sun for good exposure. Start there and then try some indoor exposures with a fluorescent shop light about 10-12 inches above the film and expose for about 6-7 minutes. Like Avery said, wash out with cool water.

Ron

The hot pink stuff

Tom in Texas wrote "I have used old style with bichromate sensitizer, have not tried newer diazo based system yet so I don't know light sensitivity on it."
Sensitivity is the same but you have to mix the entire batch up at once unlike the old Bichromate system. Anyone know where you can get the Bichromate stuff as I think Speedball has stopped making it???? With the old system and making only a few screens, a large bottle of the stuff would last for years.
The Ulano films are good but then you have to usually buy a whole bunch of it and keep it cool year round which is not always easy in a studio with kilns.
For washing out screens without a pressure washer, it is possible to get some fine details using the thumb over the end of the sink hose trick where you can control the water blast rate from a trickle to a jet.
Kevin in Tofino

[/quote]

My best guess would be at a local art supply store which might have some of the old system left.

Best wishes,
Tom in Texas

I have had screens professionally applied with a solvent wash out stencil. The reason I do this is so I can screen with water based medium enamels. When I'm done, I have the screen cleaned by the company that shot it. This way I don't have to deal with the smelly stuff myself.

Well, tonite's experiment got me part way there... After using a 60 second exposure, the design washed out just fine while the rest of the film stayed put. Only problem - I still had a ghost image from the last washout, leaving me with what looked like a double exposure (or it's time for new glasses). I used real stencil remover fluid this time so the screen's clean. Now there are two new screens drying with film in a dark, cool place (hey, that's another reason for separating hot & cool rooms as well as clean & dirty).

I wonder, tho, as I'm washing out the film starts to look very streaky - like it's going to come off in strips. Is this normal?

Yup, that's the hot-pink I'm growing to...love.
Maybe New year's gifts...yeah.

While you're washing out the stencil, check and see if the part that's not supposed to wash out is getting soft. It may need more exposure.

With more and more exposure you will get to the point where your image is way overexposed and it won't wash out.

Normally the film will change color a little when it gets wet.

Ron

If you are figuring out your exposure for the first time and wasting a bunch of film, why not waste it right? Set up your screen and then expose it in steps by covering part of the screen and moving the cover over every so often (measure the times). This way you get one screen that you can't really use but it has strips of exposure (ex: 3min, 5min, 7min, 9 whatever) One or two of those strips is going to have the exposure that you want. Then clean it up and do it again with that exposure.

next you'll want me to get a real timer instead of counting one-mississippi, two-mississippi.