Welcome to all screen printing learners here we shall tell you how photo-emulsion works and how can you use Photo-emulsion for creating a stencil on screen for screen printing.
Photo graphic emulsion is a light sensitive emulsion, it is used as one of the most common method for creating stenciling a screen for screen printing and it economical and easy too. In the screen printing there are many other method some are older than Photo emulsion technique and some are latest but none of the method have eliminated the photo-emulsion method at all because it is easy, cheap and convenient way of creating a stencil on a screen. Most of the factory screen printings rely on Photo emulsion for stenciling silk screens. Here you will learn how to coat the screen printing screen with photo emulsion.
Photo emulsion paint is a light sensitive paint; this is a very prominent property of the Photo emulsion paint that when it is exposed to light it gets hardened and become hard to remove. Its chemical composition is specific it is colloidal solution of silver halide in gelatin. Gelatin acts as folder and medium for the Silver halide (silver bromide, silver iodide etc) there are other suspended particles such as toner, colorant, etc. the gelatin acts as semi-permeable membrane for the other particle and silver halide when exposed to light become a little dark and hardened.
But before coating a screen with photo-emulsion paint a little amount of the potassium dichromate is added in the paint. It is available in liquid and powdered form, when adding it in the paint its aqueous solution is prepared and then added in the paint it act a catalyst and increases the sensitivity of the photo-emulsion paint. It aqueous solution is prepared and added it in the paint and then stirred till it gets homogenized with the paint and then the process of coating is carried on.
For the process of coating you should have:
Photo-emulsion paint prepared as described above.
A silk mesh or polyethylene mesh stretched on a screen frame having proper stretching tension.
- Take you silk screen and tape it edges so that the joint area of mesh and frame become water proof it is important for long running screen.
- Coat it with the photo-emulsion paint using squeegee, coat each of the two sides of screen twice.
- Place your screen in some dark room for drying and should be kept in dark place till exposure other wise your process will be ruined.
- Use the some dark colored paint as dark colors absorb light better than light color and you will get a sharp stencil and it also reduces the exposure time of your screen printing screen.
Watch this free tutorial video for more details.