How a photo becomes a screen print

Every Trials design starts as a photograph or a drawing, and none of them can be printed as they are. A camera captures millions of colours and continuous tone. A screen print puts down flat, solid ink, one colour at a time. Getting from one to the other is most of the work.

Here is what actually happens in between.

1. Finding the image

Most photos do not make tees. The ones that work have a strong shape that survives being stripped of colour and detail, because that is exactly what is about to happen to them.

A useful test is to squint at it. If it collapses into an unreadable grey mush, it will not print. If it still reads as something at the size of a postage stamp, it probably will.

2. Reducing it to solid colour

This is the real translation. The photograph gets separated into a small number of flat colours, because each colour needs its own screen and each screen adds cost, setup and another chance to misalign.

Continuous gradients either get simplified into bands or converted to a halftone, which is a grid of dots that varies in size to fake a gradient from a distance. That is why old printed tees look the way they do up close.

Most of the design time goes here, deciding what to throw away. A photograph has too much information and the job is to work out which fifteen percent of it was the point.

3. Making the screen

The artwork for each colour is printed onto clear film as solid black. A mesh screen is coated with light-sensitive emulsion, left to dry in the dark, then exposed to strong light with the film laid on top.

The light hardens the emulsion everywhere except where the black artwork blocked it. Washing the screen out then leaves those areas open as a stencil, and the rest of the mesh sealed. One screen per colour.

This is the step where a design becomes physical and expensive to change. A typo caught here costs a screen.

4. Registration

If a design has more than one colour, every screen has to line up exactly with the last. That alignment is called registration, and it is set up by hand before the run starts, checked against a test print, and nudged until the colours sit where they should.

Get it slightly wrong and you get a coloured halo down one edge of every shirt in the run. This is one of the two places things go wrong.

5. Pulling the print

The screen goes down on the shirt, ink is laid along the top, and a squeegee pulls it across the mesh, pushing ink through the open stencil and onto the cotton underneath.

The variables are pressure, angle and speed, and they are all in a person's arm. Too light and the ink does not fully cover. Too heavy and it spreads past the stencil edge and the line goes soft. Consistency across a run is the skill.

Multi-colour designs repeat this once per colour, with the ink flash-dried in between so the next colour does not smear into the last.

6. Curing

The last step, and the one that decides how long the print lasts. The ink has to be heated to its curing temperature all the way through, which is what bonds it permanently to the fabric.

Undercured ink looks completely finished. It just washes off, in bits, on the third wash. This is the other place things go wrong, and it is invisible until it is a customer's problem, which is why it gets checked rather than assumed.

Then it is your problem

After curing, the print is about as durable as printed graphics get. What happens to it next is entirely down to heat and abrasion in the wash, which is a short and genuinely useful read: how to wash a screen printed t-shirt.

The whole process is the reason runs are small and designs do not come back. There is more on that on the about page, and the tees currently printed are Time Loop and Golden Hour.