Does Fast Cure Epoxy Hardener Cause EPS Blanks to Gas More?

I just glassed a board with a fast hardener and I noticed that the EPS blank gasses more.  I normally use the slow hardener for laminating but I only had the fast hardener.  I spent a lot of time repeatedly pushing down the bubbles. I want to make sure that the fast hardener was the cause of the problem so I can avoid doing it again.  Please advise. Thanks

Fast is the ~25 minute pot life one?  That’s the hardner I use for everything and haven’t had an issue.

Are you sealing the blank? I only use the fast and the only gassing issues I’ve had  were when I pulled a hanging string of glass off the bottom lap and brought a bit of foam (bead or two) with it,  and didn’t reseal the hole it made.

I have found that if I route out the fin box after I lam the bottom, before lamming the deck, that I do not get nearly as much out gass issues.  I then drill out the vent plug hole in the deck before I install the fin box, and drop the vent in last.  Basically, I try to leave a hole on the side opposite of that I am working on.  (At least up untill I set the vent)

Yes in général fast hardener increased max hexotherm pic temp. Outgassing of foam increase with temp so… Époxy make for mass mold in fragile mold, are really low hexotherm take days to Harden, never became hot.

That is a good idea! Thanks

Using a small pin prick I place two small holes in the bottom lam just near the nose and tail. Lets the deck lam breath out the bottom rather than upwards through your lam. Havent had a blowout in a very long time and thats without sealing the foam too. Before you hotcoat the bottom mix up a small batch of resin mixed cabosil and push the resin in with your finger to seal the hole. Once the boards finished its very hard to see where the pin prick was made.  

Aloha Zackoopman:  that is another great idea!  Thanks for all the great hints guys!  Mahalo Dennis

Having holes for venting during cure is a very good idea, especially for those people using hot boxes. 

I drilled two 1/8" holes on each side of the stringer where the center fin box will go.  Gassing problem solved. Thanks fo all of the great tips guys!

Uncle D

genraly there is not enough free movement of air inside the blank to which putting a hole in will cure the problem of the tempreature of the blank rising that quickly.  i do alot of big epoxy eps stuf and personaly i just keep a eye on the tmpreature and make sure the tempreature is ether vary stable and not changing at all or prefurably and espesialy for hot coats is falling for a good hour or two before hot coating and that should compensate for any temprature change from glassing however i cant see even with fast harderner that would create enough heat

Hey Charlie:

You make a good point. I do all my epoxy work during a period of dropping or stable temperatures mostly in the evenings.  I normally work with PE/PU boards so I am slowly learing all the tricks involved with EPS/EPOXY boards.  Seeing those first gas bubbles on the deck freaked me out.  I know better now.


Dépend how much and how much time you let resin in bucket while you laminate. If too much stay temp increase and when you put it on blank it set faster with a higher max temp that can creat some bubbles. Faster is resin more sensitive it’s to this. Spread all resin and work it to rails quickly is the best way to go for me.

yea its amanzing how long a eps blank will contiue to out gas, and it will out gass over the intire surface which is why puting a hole in one side will not work, i leave a minimum of 1.5hours after the temp has started to drop a few deg before doing anything. a friend keeps geting the same problem and i keep bashing on about temps, you have to be patient! Glad you got it sorted i know the frustration it casuses when you just about to finnish and a bubble pops up!

That’s one reason why you must properly seal EPS foam.