Ok, I'm just kinda curious on this. I went and did my fuelproofing using epoxy thinned with 90% isopropyl alcohol (ok, yeah, not denatured stuff, but I didn't feel like buying a large container of denatured for the little tiny amount I needed). Now, it's been two days since I applied it, and while it seems to be mostly dried, the surface still seems a little, well, maybe tacky (I'd almost say greasy feeling). I am using 90 minute epoxy (all I could find when i last had to buy longer stuff), and I did thin it a fair amount, so I don't know if these come into play. And it only seems to be the surface that feels that way, it kinda feels like it's hardened up underneath, almost like it's a thin layer of scum over it is the best way I have to describe it.

Any thoughts?

When you use un-pure isopropyl you are using water too, 90% alcohol... 10% water

Water and oil won't mix, and maybe the water in the mix is "pushing" some oil from the epoxy resin out to the surface.

I guess you could try to clean that "grease" with the same isopropyl you used to get it thinned

Be gentle! or the isopropyl might remove the coating off your firewall [X(]

Saludos

Joseph

Good chance you may have thinned it more than you needed to also. It just needs to be thin enough to brush on easily with an acid brush and I usually shorten the bristles for more stiffness at the tip.

I use 30 minute epoxy mixed with iso alcohol to fuel proof and have never had any problems with it drying. I agree with Joe. maybe you put too much alcohol in and the water is pushing the oil out. It only needs to be thinned enough to be able to be brushed on. It doesn't take much. I would gently rub it down with alcohol to see if that helps, but if it seems the epoxy has dried underneath, I would go ahead and get in the air and periodicly check to make sure the coating is still there.

Good Luck

Ya, you only need like 3 drops to make the epoxy as thin as water. Thinning the epoxy make sit act different. It gets a greasy feel you are talking about and really slows down the hardening of the epoxy. You said it feels tacky, so it is setting up, just taking a lot longer probably because you thinned it down too much. I would give it few more days and see if its set by then. [8D]

I'm guessing I probably thinned it too much. I've been out in the evenings the last couple nights, so a little longer drying isn't too bad, and checking it this evening it seemed like it might be getting better. Fair chance that I won't have time to work on it until saturday, so that's another couple of days to dry still.

A better substitute is epoxy finishing resin. It's already thin enough to brush on.

I don't bother to thin it. I use 30 minute epoxy. After it's mixed, use a LITTLE heat on it. It will thin right out to brushing consisteency. Be careful, too much heat will set it quickly. I use acid brushes to brush it on.

Dr.1

DR1Driver has the best solution, I also do it that way with 30 minute or longer cure time epoxy. A little heat from the heat gun after application and the epoxy flows out smoothly, gets into the most minute spaces and cures well. I've seen many cases where alcohol mixed into the epoxy causes the problems that Piper28 has. Epoxy doesn't dry, it chemically cures and any water (isopropyl can have as much as 50% water in it) interupts or prevents this cure taking place.

No problem.

Thinning epoxy will often lead to longer curing times. Compound that with the fact that you used 90 minute epoxy and it could take several days.

But something you can do to help it along is to keep it warm - I don't mean "Midwest Summer" warm, I mean hit it with a heat gun or hair drier. Maybe you can lay it in a secluded area and aim a hair drier at it and leave it overnight, or maybe even leave it for a day in direct sunlight.

I went in last night and wiped a couple sections down with a paper towel to see if that would help. It seems to have removed any oily feeling from the surface, and the epoxy coating underneath has definitely cured, providing a nice solid layer. So it looks like things will be good. Now I just need to find the time to finish everything up.

I have done this for years with very few problems . yes, cure time may be increased. not curing at all may mean you missed on the inital 50/50 mix . the alcohol only includes water when left standing open for a period of time. the waxy felling is inherent in epoxy regardless. works very well when care is used.

I use Acetone to thin epoxy and it works real good, and does not seem to extend cure time.
-Tom