Cleaning a Screen for Screen Printing

It's important that you start with a clean screen before you start coating it with emulsion, there are two ways to clean off a screen 

Pregasol - clear liquid that you spray or brush on the screen, this removes the emulsion

Pregan paste - This is an alkaline paste that should only be used if you need to deep clean your clean, by this I mean removing build up of emulsion and removing ghost images (though you can purchase Pregan anti-ghost which is made for removing ghost images). I use the Pregan paste about every 3-4 months, as it is an alkaline and in corrosive I wouldn't recommend using this every time you need to clean a screen (thats what pregasol is for). care should also be taken when using this product as it can cause burns if it comes into contact with your skin.

Green bottle is Pregasol and then Pregan Paste on the right.

Firstly I take my screen outside (I don't have the luxury of a wash room) and I spray the pregasol onto the screen and leave it for a few minutes to sink in.

I then use a pressure washer on full power to clean off the emulsion and screen filler (the red lines on the screen). The pressure washer has to be on full pressure (one jet) so that it can pass through the screen to remove the emulsion, if you have the washer on half pressure you will be standing there for a very long time as there is not enough pressure to pass through the screen (you'll only be washing the surface).

I normally clean the screen in lines, so what I mean is that instead of just moving the jet all over the place I start in the top corner and move down the screen and back up to create lines. This way you should get all the emulsion off and it's quicker.

Note:

Full Pressure (one jet) - to remove emulsion

Half Pressure (two jets) - to wash off ink after printing 

Hold the jet as close to the screen as possible (I normally hold it about 2cm away from the screen) as it will be more effective in removing the emulsion than if you stand 3 ft away.

9 times out of 10 you won't get it all off in one go, especially of you have screen filler on the screen. To clean the stubourn patches off you just simply spray some more pregasol onto the areas and then wash it off.

Afterwards you'll be left with a clean screen and all you need to do is let it dry.

If you are not too sure if your screen is clean or not hold it up the light, if you can see straight through it then all the emulsion is gone, though if you can see some green/blue specks in the screen then there is still some emulsion left on the screen.

In some cases you'll be left with a ghost image on the screen of what ever was on there before, don't worry this shouldn't effect your print in anyway. As you can see on the screen below I have the ghost images of two previous projects, the way to remove these is by using pregan paste.