WHAT ARE DIRECT FILMS?In case you aren't sure just what a Direct Film is, here is a quick overview. Direct films are light sensitive stencil "films" that are made of a clear carrier sheet with a light sensitive emulsion coated on it. Direct Films are sold by the sheet or by the roll and are designed to be ADHERED TO THE SCREEN WITH WATER, dried, and then exposed just like a direct emulsion. These films are also called Capillary Films, or Capillary Direct Films - because the emulsion on the clear carrier is drawn up into the wet fabric through capillary action.
DIRECT FILM ADVANTAGES
Direct films are obviously quicker to use because you can adhere the film to a WET SCREEN THAT HAS JUST BEEN DEGREASED. This eliminates the drying step needed with direct emulsion! It also eliminates the drying step between multiple coats of direct emulsion. A single direct emulsion screen could take up to an HOUR OR TWO to make because of the drying, while a direct film screen may only take 20 to 30 minutes. Another real advantage to direct film is the sharpness of the image edge. Because the film is adhered to the bottom of the screen it gives a very smooth surface. This enables you to reproduce a very sharp print. This is not as noticable on a knitted T-Shirt but on a non-absorbent item such as heat transfer paper, metal, or glass you can really see the difference in print quality over a direct emulsion!
Direct film is sold in various film thicknesses. These range from 15 microns all the way to 84 microns. For general T-Shirt printing a 35 micron works good. If making heat transfers you should use at least a 40 micron and preferably a 70 to 84 micron just to lay enough ink down for a good print.
The real beauty of direct film is that your exposure time is ALWAYS THE SAME (within the same film thickness)! The mesh count or color doesn't have a bearing on the exposure. If you are looking for consistency then this is it. The drawbacks (yes there are some) to direct film is that it costs more than direct emulsion. This extra expense is really a moot point when you consider the LABOR SAVINGS OF USING DIRECT FILM. The other drawback, is that it occasionally doesn't work and is harder to use on finer meshes. It does require a little more getting use to but once you get it down I think you will really like it.
15 TIPS FOR CONSISTENT RESULTS WITH DIRECT FILM
- The screen MUST BE thoroughly degreased. It needs to really hold water for the film to adhere best. A roughening agent such as 500 grit silicone carbide, or degreaser with a roughener works good. Some suppliers now offer a WETTING AGENT to use to help the screen hold water. The more water the screen "holds" when you are adhering the film the better and more consistent your results will be.
- The film is light sensitive and should be used under subdued light, yellow bug-light, etc.
- The film is adhered to the bottom of the screen by laying the wet screen down ontop of the film and then doing a quick squeegee stroke across the screen. It can also be adhered by rolling the film onto the bottom of a wet screen (my preferred method).If the screen is really wet the film will draw right into the mesh like a magnet.
- Always have a spray water bottle handy. If you see areas where the film did not adhere (immediately after application of the film to the screen), spray that area with water.
- Dryer the screen in a dark area with a fan blowing across it.
- Make sure the film is thoroughly dry before you expose the screen. It should take about 20 to 30 minutes depending on your humidity level. Before exposure, peel off the clear carrier sheet.
- If you are using undyed emulsion now - try doubling your standard exposure time with direct film. An Exposure Calculator is idea to determine the correct time.
- Wash-out the screen from the bottom (underside). It may take a little higher water pressure to remove the unexposed film.
- If you have exposed the film correctly it should be durable during wash-out. If the film starts to peel away you may have underexposed the screen or not properly degreased the fabric. Proper exposure time is more important with direct film.
- When working on meshes of 230T or higher, roughening and proper degreasing are VERY IMPORTANT. It may also take a little gentler wash-out because the film does not grip the finer meshes as good as the coarse.
- You can combine DIRECT EMULSION and DIRECT FILM to make a very durable screen. Simply bring a DRY screen down onto a piece of direct film and spread direct emulsion on the inside with a squeegee. The emulsion acts like the water and helps adhere the film to the screen and also makes a more durable screen.
- "Filmed" screens can be stored for a number of weeks in a cool, dark place before use.
- Direct film screens are very durable. In fact the manufacturers say they will withstand 30,000 impressions!
- If using a water-based ink make sure to use a water-resistant direct film.
- Be careful if taping over image areas on the bottom of the screen (when using a ganged screen). There is a chance that the tape may pull part of the film away - especially if you have stored the screen taped, and untaped it weeks later.