Quickie Q2 Lite, Construction Manual, Page: 33 / 299

..... The working and strength characteristics of an epoxy system are
dependent on the resin, the hardener, and on the amount of each in a
given mixture. Epoxy systems are engineered for a specific ratio of
resin and hardener. It is quite important that the proper mixture be
obtained. An accurate balance or ratio pump must be used to accomplish
this. A drawing of an inexpensive ratio balance is included in these
plans. The mix ratio accuracy is particularly important with Safe-T-
Pox. The 5-Min. can be adequately rationed by merely pouring a blob of
part A in a cup and adding a blob of part B that looks the same volume
before mixing. Never eyeball estimate Safe-T-Pox, always carefully use
the balance or pump.
..... Epoxy resin and hardener are mixed in small batches, usually 6
ounces or less, even in the largest layup. The reason for small
batches is that, in large batches, as the hardening reaction
progresses, heat is generated which speeds the reaction, which causes
even more heat, which ends up in a fast reaction called an exotherm.
An exotherm will cause the cup of epoxy to get hot and begin to
thicken rapidly. If this occurs, throw it away and mix a new batch.
The small volume batch avoids the exotherm. For a large layup, you
will mix many small batches rather than a few large ones. With this
method you can spend many hours on a large layup using epoxy that has
a working life of only a few minutes. If the epoxy is spread thin as
in a layup its curing heat will quickly dissipate and it will remain
only a few degrees above room temperature. However, in a thick buildup
or cup, the low surface area to mass ratio will cause the epoxy to
retain its heat, increasing its temperature. This results in a faster
cure causing more heat. This unstable reaction is called an exotherm.
Exotherm temperatures can easily exceed the maximum allowable for foam
(200°F) and damage the foam-to-qlass bond.
..... Unwaxed paper cups are used for mixing and ratioing resin and
hardener. Convenient 8-oz cups for resin are provided. The hardener
cups are the 3-oz unwaxed bathroom paper cups. Don't use waxed cups;
the wax will contaminate your epoxy.
..... If you are using the homebuilt balance, follow this procedure.
Place the resin (8 oz) cup on the right cradle. The resin cup can be
either a new clean cup, one with a little uncured epoxy left in the
bottom, or a clean cup from a previous layup with hard epoxy in the
bottom (smooth, not lumpy). Now, take a clean 3-oz hardener cup - pour
a splash of hardener into it then scrape the hardener back into the
container. This gives the hardener a wet surface, so its remaining
hardener will not be counted in the balancing. Now, place the wet
hardener cup on the scale, check that it swings freely and balance it
perfectly by moving the small weight. Epoxy is then poured into the 8
oz cup (6 oz or less). Hardener is then poured into the 3 oz cup at
the other end of the balance until the arm is level. When ready to
mix, pour the hardener into the resin cup and mix completely. If you
have the ratio pump, you simply put one cup under the spout, pump out
the amount that you want and mix.
.....
Mixing is done by stirring with a stick, being careful not to spill
any. If you spill part of an unmixed cup, the ratio of resin and
hardener may be inaccurate and it shouldn't be used. Mix each cup for
at least two minutes. You should spend 80% of your mixing time
stirring the cup and 20% scraping the sides to assure complete mixing.