Learning Screen Printing - The Photolith

What is a photolith?

The photolith is one of the fundamental pieces of the screen printing process. If the photolith is poorly printed, then the final finish and detail will not be what we want.

The photolith is a transparent plastic sheet, usually made of polyester, where the design we want to print is printed. It is always printed in black. It is similar to the slide reflected in projectors, or like the photographic film inside the roll that is then transferred with light to what is the photo.

And can I make photoliths at home?
Many will tell you no, but in 90% of cases, depending on your design, you can make the print at home or at any copy shop.
For screen printing, it is enough that the black color of the photolith does not let light pass or lets very little pass. It is not necessary for it to be 100% black when seen printed.
If our design is VERY complicated and with A LOT of detail, I would recommend going to a professional place to make the print. For example, if you want to make a screen print with very small letters, like the number 5 in Word for example, very very fine lines, or if you have to make prints of 2 or more colors with detail and need everything to align perfectly.

To make photoliths, just print on our home printer on acetate paper. You can buy it at any stationery store. A pack of about 15 acetates costs no more than a couple of coffees.
I usually print them at a copy shop near the workshop since they have printers that handle A3 acetate without problems. It costs around €1.20 at the copy shop I go to. Depending on the design, I take it to specialized places ($$$$).
Another option, if you don't like acetate paper, is to print your photoliths on tracing paper or onion skin paper, it is semi-transparent and lets light pass when exposing. I really like this option because it allows drawing directly on the paper and gives another texture.

A trick to make our homemade photoliths even blacker is to use a toner opacifier spray. They work great! I hope to have it soon in the online store :).

Remember that on the photolith we must print in black the part of the design where we want the ink to go.


Photolith printed on polyester sheet to make electrical circuits. Photo from the forum Aeromodelismovirtual.

Photolith made with onion skin paper and by hand. Also called tracing paper or vegetable paper. Photo from the blog of Las paranoias de Misaoshi.

The photolith is still used to make different types of screen printing.

Another option, MacGyver style, is to print your design on a normal white sheet of paper and coat it with oil using a sponge, let it dry until we see the paper becomes transparent and does not stain. I recommend reviewing the printed drawing once it is dry.

How do you usually print your photoliths?