HOW TO CONSTRUCT THE PLASTIC FRAMES

	These are the instructions from Dave Burk (X-3235) on how to
construct the plastic frames of our detector:

- Clean the mold from any flashing. The molds are made of RTV (Shin-Etsu
KE 1310 ST) and you can use a piece of wood, alcohol and acetone to clean
it.

- Put some mold release (MR300) inside the mold. The spray should be used
inside the distillation hood fan. Do not put it too often because it makes
the frames to loose precision. After you spray the mold release, brush
around.

- Close the molds. For the small one, put a rubber band close to the top.
For the large frame mold put the 7 brass rods across and finish with the 2
acrylic plates. Be careful to avoid deformation.

- Start making the polymer. You have at most 15 minutes to do that before
it starts curing. You should use the UC40 from Conap. UC40-A is a urethane
prepolymer and UC40-B is the curative. Note that UC40-A is water sensitive
so back fill the can with nitrogen each time you refill the small jar.
UC40-A and B should be used in the proportion of 2(A):1(B). First of all,
mix the  UC40-A with 2 % (2 per hundred of resin) of the black dyer
additive. Like a good dry martini, please stir, do not shake it!  The
large frame takes ~ 62 gr. and the small one, ~13 gr. So use 50 gr. of
UC40-A and 25 gr. of the UC40-B.

- Assemble the funnel plus the plastic tube in each mold and fill with the
mixture on the top of the scale.

- Put the molds in the vacuum bell. Let it stand in an angle with the
horizontal and cover with a plastic bag. Close the air valve
(perpendicular to the pipe) and open slowly the vacuum pump (parallel to
the pipe). Let is reach ~ 0.5 atm. Shut down the vacuum and start opening
the air very slowly. If something gets wrong, do not try to clean the
mold. Let it cure first.

- Do not take the frames off the mold before 12 hours (best 24 hours)
otherwise the mold itself can be damaged. To cure in the oven is faster
but we loose precision.

Sergio & Eduardo