Complex chemistry solved with a simple fingerprint. No – this isn’t some funky TV cop drama. This is using a fingertip to assess whether or not the first pour of epoxy is ready for the second pour. Here is the (no doubt) thrilling image that explains this topic.
That’s my fingertip and my fingerprint showing on a still wet coat of epoxy that is mostly saturating the fiberglass on the blade. First of all, you can still see the fiberglass cloth weave to the right of my finger. That means the cloth is not saturated. The weave you can NOT see in the rest of the pic is (more or less) saturated from that first pour.
The big question is WHEN DO I POUR A SECOND COAT OF EPOXY?
The easy answer is to just wait until the next day when you can scratch up the freshly hardened surface and pour on the second coat. The accepted theory is that this is a ‘mechanical’ bonding process between the old and new epoxy.
The ‘other’ accepted theory (mostly anyway) is what I am doing in the picture. In the time frame of the image, I’ve been checking the blade surface every few minutes with a fingertip. Prior to this picture, I had checked a couple of times and still had epoxy adhere to my fingertip – meaning it was too wet for the next pour. The third check (pictured) my finger still left a mark, BUT came off the surface dry and not sticky. In that small window of time when the first pour is still wettish but mostly dry, is when you can pour on a second batch (aka a hot coat) and achieve a ‘chemical’ bond between the two layers of epoxy.
I can’t say when this window of time occurs because conditions vary and that makes each pour different.
If you want to try this, get a rag and a second cup of coffee (or an adult beverage), maybe find the great version of Althea that John Mayer D&C did at a 2018 concert, and WAIT. Check every minute or two until your fingertip leaves a mark, but lifts off the surface dry and clean. I then mix a three teaspoon batch of epoxy and pour it on the areas of concern and move it around (I use a fresh brush) until it is blended in with the first pour.
If you are building a quietwater paddles kit (or wavetrainSUP), do this on the first paddle first side. That way you have the second side to confirm/correct your technique and a whole second paddle to more confidently do this method again. Really, ALL you are gaining is time savings. If this seems too risky, just let that first pour harden and then add the second pour.
Enjoy the build and then go enjoy your shiny new paddle in something wet!