Over the years I have done a lot of repairs and fixes with epoxy, and my favorite way of getting a smooth surface which requires no sanding is to tape a piece of clear plastic wrap over the fix.
My question is what is the proper time frame to leave it covered ?
I usually remove it overnight, but have often wondered if that is Ok or if I should leave it longer?
jackL
Its ok to leave it longer.
I’ve left it on for a week whle the epoxy cured.
Wax Paper. 48 hours.
I need to rephrase the question.
what is the shortest time.
For instance is overnight ok ?
JackL
In my experience
I have not been able to strip the wrap from the repair until the remaining resin in the pot has gone off. Any attempt to remove it before then will result in failure. If the thin layer of resin on the side or bottom of your mixing pot has become sufficiently hard, the repair should be as well.
Jim
but if it is thin . . .
Good advice, but a thin layer will cure more slowly than a thick layer. As such, if you have a larger quantity left over in the pot, it will cure much faster than your thin repair.
Other factors include the temperature, the resin and hardner used, and the ratio they are mixed.
It seems, though, that since the plastic is just to make it smooth, as long as it seems firm you could pull it off.
I usually test the set by pushing with a
fingernail against the food wrap film, out toward the border of the repair. If it’s pretty hard, the film will pull free easily. I imagine that the amine blush on the surface helps the film to pull free more easily. After many repairs, I can’t recall having removed the film too early, or having a problem because I left it on too long.
One thing is not a suburban legend, though… If you use the original version of Saran Wrap, it may not pull free properly. Just generic, cheap, food wrap works.
Time…
Overnight sounds about right… If it looks OK then it is OK. I won’t be fully cured for days but gentle use is fine. Curing time depends on temp and speed of part B, you could do a control sample on a scrap to give you an idea of timing.
Jack, just peek under a corner or plop
a little on a separate piece of saran on the table right next to it. You can pull it anytime it will come off and the epoxy will cure just fine. For broad surfaces, try 4 mil unwrinkled plastic … works perfect.
Thanks all
– Last Updated: Dec-16-08 2:31 PM EST –
I believe that is what I am using Pat.
it is stiff plastic film that is used as dividers in three ring binders.
The reason I asked is I shortenend an Epic paddle, (sorry Pat I like your paddles better, but I figured why let this one go to waste) and let them go overnight.
Used the same pot of stuff on both, and one was completely dry when I peeled it in the morning, while the other one was tacky.
jackL
Thamks Rick,
That is about what I was figuring, but wanted you pros to confirm it.
Get ready for some paddling, we are heading down your neck of the woods, (paradise) shortly
jackL
Sounds good Jack…
I changed boats so I’m ready for anything… 
using a plastic film over epoxy
AFAIK, is a way to prevent that so called amine-blush.
because the epoxy cannot have a reaction then with the water and CO2 in the air.
Technically 1 minute
Perhaps you are confusing epoxy with polyester - which sometimes needs an air inhibitor to harden according to what type you buy. The over-the-counter bondo or body shop stuff in a can will harden open to the air. Epoxy doesn’t need any of that. So technically, if you are using epoxy putty, you could press some Seran wrap on it to smooth it, pull it off and go watch TV. If the epoxy is thinner or sticky, then you would leave it on because pulling it off will pull peaks on the surface.
Who puts plastic over any resin , and …
… why in the heck would ya ??
I know , so many here is the answer , right .
Absolutely no need for it , or benefit from doing it whatsoever … all top coats (last/final) are performed with waxed when using esters (poly/vinyl), and when using epoxy (which is a gizzillion times less sensitive to temp. and humidity) , use “slow” cure hardner to prevent blush , or just rinse it off w/warm water and wipe when using med.-fast .
Never do an epoxy job over 78* ambient , no matter which cure rate part B you use . But you can do epoxy work down to about 35* . Polymerizing epoxy is virtually unaffected by humidity , no so with esters .
There are different viscosity resins also . And if you need/want fillers , wood flour , cabosil or microballons are all that is ever needed , unless structural , then maybe chopped strand added too .
The funniest thing I ever heard of was here on pnet. , putting plastic over gelcoat , what a hoot !!
esters = non-waxed for (tack coats) layup or gel , waxed for final coat is the proper proceedure .
It’s not for the blush
It’s a quick way to ensure a smooth finish (no runs in epoxy or wrinkles in fabric). Keeps the final sanding to an absolute minimum.
Pilot?
"…The funniest thing I ever heard of was here on pnet. , putting plastic over gelcoat , what a hoot !!.."
Ummmm, using plastic film or stretch-wrap has been SOP for making repairs and modifications (think: Kevlar skid plates) smooth for, oh, I dunno, 40 years or more. Are you confusing this technique with something else?
Jim
I’ll use plastic wrap, and you can sand
cheers,
JackL
… on that note… Epoxy is V E R Y
effected by humidity and moisture during the cure phase. Carbon, glass, kevlar, etc too …
What are you doing reading P-net …
when you should be working on my paddles ?
Cheers,
JackL