On Sun, 15 Dec 2002, Olin Lathrop wrote:

*>I have no idea how things may have changed in the last 22 years.

I'll try to describe the P20 photoresist spray from Kontakt that I used
till recently (1year ago):

It's a small spray can with instructions on it. One component. You clean
the board, preheat it to about 60C and spray one layer from about 20cm in
one pass. The layer will be pale green (the liquid is dark green). This is
done in subdued light.  After 5 minutes (while still keeping the board at
60C) you spray a second layer as above. Then you leave it be at 60C for an
hour or 70C for 30 minutes. That's it. After this the board can be stored
up to a few months in a cool dark box or exposed immediately. Exposure is
about 5 minutes with normal UV exposure lamps (350nm Hg vapor) through 1
sheet of 3mm glass frame and transparency artwork (laser printed). The
developer is 4 grams of lye (NaOH) in 1liter of tap water. The development
is done in 1 minute or less, leaving the green layer only where there was
no light. After this you can etch with FeCl3 or something else. The resist
comes off with acetone or nitro paint thinner. The spray bottle covers
about 10 square feet and keeps for 1 year or more. The chemicals are not
so nasty excepting for the solvent vapor that MUST be fanned away. I have
used a full face mask respirator for this before but a vent is better.

The datasheet and msds sheets are on the web (long line paste carefully):

http://212.166.5.17/csp/web/DSlst.csp?lng=3&country=BE&product=POSITIV 20&brand=KOC&SCAD=208206042541

Kontakt Chemie is a brand name of CRC Industries as you can see. They say
the color is blue but mine is actually bluieish-greenish and the layer on
the board is definitely green. The artwork appears yellowish green
(faintly) on the flatter green of the layer after correct exposure and
before development.

Peter

PS: All the horror stories about this material on the web have to do with
the fact that nobody I heard of uses a preheated board - which is
essential. If the board is not heated then the drying resist will build up
a lot of charge from the departing solvent and will form holes and
mountains on every piece of dust it can attract (and it can attract them
all, even from a completely clean washed plastic food box with a
hermetic lid). With the heat on drying is so fast it has no time to do
stupid things and it works great.

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