Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Painting, Finishing and Care. => Topic started by: douglas g on July 12, 2018, 12:09:28 pm
-
Three days ago I applied a final coat of Z-Poxy finishing resin to a plywood boat hull using what was left of two bottles of resin and hardenener that had been open for just under a year. However, the resin does not seem to be going fully hard - it seems rather waxy and is still sticky to the touch. I did make an effort to mix it carefully.
Has anyone any advice what to do and what is the cause? Is it perhaps because the bottles have been opened for so long?
I am planning to leave the resin longer to see if it hardens slowly. At present if I try sanding it, rather than creating dust it clogs up the abrasive paper as it is sticky. As the product guide mentions the use of heat to accelerate curing, I was wondering about using an electric heat gun, but I am worried about damaging the wood underneath.
-
Put it in the airing cupboard, if you have one, and leave for a week (ish). I had this problem some years back and this solution was recommended to me. Worked a treat.
-
:-)) Thanks for that. I'll give it a go. With the warm weather we are having, I am surprised the heat in the conservatory where the boat is hasn't already done the trick. I have seen cold temperatures suggested as a cause of slow curing in epoxy products.
-
If it's been left too long once mixed it will never cure. For epoxy to set well it needs to be kept warm (e.g. room temperature) for 24 hours after application. Once set it should not be sticky at all.
Epoxy has a very long shelf life I find, but I've not used that brand. You do need to be very accurate with mixing quantities, I use a fine digital scale. To see if your epoxy has gone off, try mixing a small amount , and apply it to a piece of scrap timber, and see how that feels the next day. If it's sticky,it's probably the resin.
-
One of the advantages of the Z-Poxy resin is that you mix equal quantities of resin and hardener, so the proportions are easier to get right. Searching Google, I have found one or two other reports of the same problem with this product. The suggestion there seems to be to give it time or remove with acetone and start again (don't fancy that...)
-
After trying heating with a hair dryer with no effect, I have had to accept that for whatever reason the chemical reaction isn't gong to happen resin just isn't going to set. Luckily I have found that with copious amounts of methylated spirits and a lot of rubbing with a rag, the uncured resin is coming off. It has the consistency of adhesive form a sticky label. Hopefully once dried off a final sanding should remove the last residue. Without the meths first, it was just clogging the abrasive paper.
-
Did you try mixing some more and applying to a piece of scrap timber to see if it sets okay overnight? Good weather for drying resin!
-
No, it was the last of those bottles. I am not going to keep them open for more than a few months in the future. It was very hot when I mixed it up and applied, so it can't have been the temperature.
-
I love Z-Poxy, but have often wondered that when both bottles are less than a third full if the air left inside can inhibit its effectiveness, especially after a couple of months after being opened.
Luckily I tend to use it up before then.