How to Avoid Gelcoat Wrinkling (Alligatoring) What to Do, and what NOT to Do!

In today’s video we are going to show you how to hopefully avoid the wrinkles in gelcoat which are sometimes referred to as Alligatoring or pickling of a gelcoat.
* some further info.... As quite rightly mentioned by one of our viewers, we are showing what the ideal temperatures and dosages are for resins. We don't however explain how you can increase catalyst dosage to compensate for low temperatures, this is because we do not know which polyester system you will be using and some polyester resins behave differently and it depends on their intended final use. For example tooling or chemical resistant resin systems should never be applied at low temperature as they usually need an initial ambient cure followed by a high temperature post cure to reach their optimum chemical resistance or high temp resistance. It is always best to speak to your current supplier about the resin you are using before deciding to go against the product's data sheet recommendations.
You usually need your second layer of gelcoat or resin to cure within an hour at the very most. for most general purpose resin systems this would be achieved at approx 15-20 deg C by adding around 2% catalyst, between 10-15 deg C add approx 3% .
For sheathing work such as GRP roofing or general repair you can work at 5-10degC with around 4% or 5% catalyst addition, we just wouldn't recommend going this low for moulding applications. even a slow curing first gelcoat can attack some release systems.

[@mohammedabo-riyash866]

Thank you very much, sir. I've faced this problem myself and till before this video, I couldn't have figured out why this happens. We've searched and searched for days and never got the answer. Appreciate this video.

[@ecfibreglassuk]

Thank you

[@monkeybase01]

This has been my biggest frustration. Very informative!! Thank you for explaining the reason why this happens! :)

[@ecfibreglassuk]

You're welcome!

[@zellalmohammed406]

Thank you ❤

[@DavidMalenczak]

So is it recommended to have a bit of air circulation like a desk fan blowing across the part? No heat just air moving.

[@ecfibreglassuk]

This is one method purely to help release the styrene from the deepest parts of a mould, it doesnt have to be a fan you can even fan it now and then during curing with just a peice of card or simply turn the mould on its side to let the styrene vapours out. This is because styrene is heavier than air and will lie low on moulds slowing down the cure. In terms of temperature it is best to work between 15 and 20 degC and avoid direct heat on the mould has this can create other issues such as hotspots leading to severe shrinkage and pre-releasing which can cause indentations in the final part.

[@BeatenRustBuckets]

Honestly this is more of a ideal conditions situation. With gell I have sprayed it as low as 10 deg F on multiple days with no issues at all and even colder with resin when laying up. You may have been better off giving a sliding scale showing MEK percentages verses temp and humidity if you really want to help out people and how having wax added to the resin will change the curing rate. All in all I get what you were trying to do this is just my 2 cents on what could help out with some more real world applications.

[@ecfibreglassuk]

I totally agree with you and I appreciate your feedback . Most manufacturer's material data sheets suggest temperatures should be at least 18-20 °C with a minimum 2% catalyst. Some users will push the boundaries, and I admit I have done that myself, such as increasing catalyst and even stealing my wife's hairdryer to encourage laminates to cure in my cold shed at home😁 , and I've very rarely had any issues apart from the odd pre-release marks at times from too much direct heat or curing too fast causing shrinkage. Although, if you do work outside the recommended parameters and the moulding pops out with defects, then you have no quarrel or cause to complain to the supplier or manufacturer of the material even if you have got away with it previously in the same cold conditions. As a responsible distributor of our suppliers’ materials, we can only demonstrate how to use these materials as intended and recommended by the material manufacturers guidelines. Customers are more than welcome to experiment with extra catalysts and methods outside of our advised recommendations as i have done in the past, but it is at their own risk.