ORIGINAL: Campy
1. Rubbing/Isoprophyl alcohol contains water. Use DENATURED alcohol or acetone to thin.
Arrgh!
YES corrected!!!! Thanks.
That's what I should have said!
Denatured Alcohol is what you purchase at a hardware store.
ORIGINAL: Campy
2. Do not thin more than 10% BY VOLUME. More than 10% and you have a very high probability of the epoxy not curing properly (or curing at all ).
I've never had problems all the way up to 30-40%, especially for this use, namely fuel proofing.
However better to err on the side of caution.
ORIGINAL: Campy
3. Heat (via a heat gun ) is your best bet for thinning the epoxy. It is safe and will thin the epoxy very nicely.
It's a bit harder to "stretch" the epoxy this way. Not that it doesn't work.
I normally fuelproof the firewall area and just behind it with the strongest epoxy mix. Then use the thinner mix ( 30% ) to do all of the reachable wood surfaces within the fuselage that I am not otherwise re-inforcing.