Date: Tue, 17 Jul 2001 11:58:06 -0400
From: Marvin Kaye <74740.231@compuserve.com>
Subject: Re: Color in Jefco
Sender: Marvin Kaye <74740.231@compuserve.com>
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Posted for David Jones <N295VV@aol.com>:

Color development in organics over a period of time is usually tied to 
degredation by light.  It can also occur from reaction with metal--the tin
or copper in brass, for instance, called chelation.

In either case, a few ppm of chemical forming double bonds or grabbing off
a few atoms of metal can give an intense dark color.

I feel that the loss in bonding characteristics at this micro of a few ppm
level is insignificant.

The appearance of color is not limited to Jeffco, as it occurs in the Teta
system as well.

Most pure organic chemicals are best stored in the dark, thus the use of 
amber colored bottles in the laboratories where they are used.  If you use
a light bulb to heat your pump area, you, of course, are defeating this
rule.

Perhaps an aquarium heater immersed in a jar of sand might serve the
purpose without emitting the naughty little photons which are causing this
discussion? 

 It also will be a little safer from a fire-starting stand point.  I always
worry about hot light bulbs starting fires.

Aquarium heaters have their own thermostats, as well.  But do not immerse
the heater in a jar of water.  Use sand.

Rather than being overly cautious about color development, you need to be
very careful about exposure to moisture.  

Those of you in humid climates need to be very vigilant about keeping the
wet layups from being exposed to moisture.

When you start to see a white film on the top of your freshly prepared 
glass/epoxy layers, you are getting degredation from moisture.  Some people
call the Amine Blush.  I call it watery epoxy.

To minimize this in wet weather, we used to roll out a very thin layer of
plastic on the top of our sandwich, and then leave it in place after
working out the bubbles.  The next morning, we would peel the plastic from
the cured layup.

The problem is, of course, that if you fail to remove the protective
plastic layer, subsequent layers are useless.  For this reason, a lightly
colored plastic should be used, so you can make sure you can see it, and do
not forget and leave it in place.

If you live in a wet climate and see Amine Blush on your layups, be sure to
sand hell our of the cured surface before  applying additonal layers.  This
whitish surface has absorbed huge amouts of water, and has practically no
ability to bond with subsequent layups.

Sanding a surface that has been contaminated by moisture will yield large
crystalline chunks of debris, which sometimes look like sugar crystals. 
Sand hell out of the surface until you see no more of this.

The use of one or two dehumifiers in your shop area is recommended for wet
climates. Be sure to drain the condensate outside of your building.

I used the Teta system for my plane.  If you live in an area where you
cannot get away from moisture, you may want to consider switching to this
system, since it wets the glass much faster, and is faster in working out
the bubbles, making exposure to moisture minimized if you keep things
covered.

Happy building.

David Jones
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