What is the use of the Diazo which you supply with the emulsion?
the small bottle of DIAZO is used to make the gelatin photosensitive. If the Diazo in not added, the gelatin on its own is not photosensitive, and therefore it does not harden with the light and it comes off during the exposure.
How long can you keep the emulsion frames?
The emulsion frames have to be stored in complete darkness and in a cool place. In this way the can be stored for about 30 days.
Are the emulsion and the engraving the same thing?
No, they are not the same thing. They are two subsequent phases for the praparation of the screen printing machine The spreading of the emulsion has to be done on a stretched frame, in order to make it sensitive to UV light. In dorder to do so, you need to use a scoop coater to alternatively spread the emulsion of the two sides of the frame. Afterwards the frame has to be placed again in a horizontal position, print side down, in a dard room (a wardrobe or a frame drying rack). Once the emulsion is dried the frame is ready to be engraved: in order to engrave, the film image matrix has to be applied, on the printing side, gelatin against gelatin; by means of the suitable UV light exposure unit, after creating the pneumatic off contact which allows the film to perfectly adhere to the frame, it is then exposed to the UV light for the necessary time. This is the engraving. The following process is the exposure, which takes place in running water and it serves the purpose of melting the gelatin which has not been exposed to the light, the one corresponding to the engraved image.
What happens if I overexpose the gelatin?
What happens is that the eccess of light closes the finer lines of the engraving, and it is no longer possible to remove the gelatin. If one increases the exposition even more, it becomes impossible to remove the gelatin at all.
How long does the opened emulsion last?
If it is kept in the fridge, it can last up to 3 months.
This is Franco Ratto,