Once your screen is ready, it’s time to mix up some photo emulsion and apply it to the screen. I did this in a really haphazard way, and through trial and error managed to work out the right way to do it. I find that most tutorials you read are handy, but they never explain all the things that you can do wrong, and you are pretty likely to fuck up a couple of times, so I thought it would be helpful to show my errors so that others can learn from them without making the same mistakes.
NOTE: due to working with light sensitive materials all the following procedures must be done in subdued light – it doesn’t have to be like a dark room or anything, just make sure the curtains are closed or do it in the evening with a fairly dim lamp on.
The first thing to do is mix the emulsion. Different brands will vary slightly in their directions, but they’re mostly the same process. Basically, you have some emulsion (big pot of blue paint-like substance) and some sensitizer (little pot of dirty yellow-green powder) which have to be mixed together. The powder needs to be dissolved in some water before being mixed with the emulsion. As long as you do those two basic steps with approximately correct quantities you’ll be alright.
First it is best to decide how much emulsion you want to sensitize. It is easiest to mix the whole pot in one go, but since the emulsion lasts about a month sensitized and about a year unsensitized, I didn’t want to use all of mine in one go, so I decided to mix a quarter at a time.
Tip out your sensitizer powder onto a bit of paper and roughly divide it up into heaps (in this case four):
Next, measure out the right amount of emulsion and pour it into a mixing pot. It’s a good idea to get some lightproof pots/jars to keep the mixed emulsion in, or make your own like I did. Here’s 250ml (quarter of the litre pot) of emulsion:
After already making quite a lot of mess, I then proceeded to completely forget what I was supposed to be doing, and mixed the powder directly into the emulsion:
The correct thing to do is to pour one of the four heaps of powder into a little pot, mix with a small amount of water (about 25ml, or a UK single shot glass) and then add it to the emulsion.
Then mix it in thoroughly. You should notice a change in colour towards a darker blue-green colour:
I mixed another quarter pot afterwards with the correct method, and there didn’t seem to be much difference between them so I imagine if you fuck up and mix the powder straight in like I did, it will most likely still be useable. Make sure your pots are pretty light-tight, and label them with the date they were mixed so you can use them up before they go off later. These can be put in the fridge and used for the next 4-6 weeks.
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