A decent film positive is an essential part of achieving a great stencil as part of the exposure process. A simple test is to hold your film positives up to the light … if the light can be seen through the artwork then the positive is not dark enough – we do not want the light getting through the artwork when exposing.
So some tips…
Double up on your film – print out 2 copies then cut the corners off one of the films, line them up and stick together with invisible tape. Make sure that the film positive is nice and tight against the screen when exposing especially if your exposure unit does not have a vacuum.
Use decent film positive paper, inkjet film is coated to ensure that ink completely adheres to the paper which in turn makes the artwork darker.
Get yourself an Epson – they seem to be the best at putting down more black than many other brands. The Epson 1500W is rather good – use the blacquer ink system which is designed purely for making film positives – it’s very cost effective and does the job.
If you are using a laser printer then buy an Epson 1500W (sorry showing a bit of a personal preference there) but seriously if you are using a laser then you can use a toner density spray which makes the artwork darker. The old technique was to paint oil (vegetable most popular or white spirit) over the artwork – but rather unpleasant!