I do a good bit of repair/restoration work and use a fair amount of epoxies for wood repair. Acraglas is one of my go-to's.

The set time can run into 8-12 hrs though and not be appropriate for the type of repair being done. Recommended mix ratio is 4 parts resin to 1 part hardener.

This is great when you want the epoxy to run into the depths of a crack or need extended working time for bedding. But if you want to glue on a splice or quickly mend a small split it can be a hindrance to shop time. By varying the ratio of resin to hardener you can control how fast it sets. The following are ratios of resin to hardener and approximate set times that I have determined through experimentation:

1:4 - 8-12 hrs
1:3 - 2-3 hrs
1:2 - 45 min -1 hr
1:1 - 10 - 20 min

I hope you find this information useful. As with all epoxies the higher the ratio of hardener to resin the weaker the bond, but even so it is more than adequate for most repairs.

Bob
www.rustblue.com

Good info to know Bob, thank you.

Very useful information. Like you said, there's some applications that don't require the full strength and would benefit from faster cure time. I've always kept 5min epoxy around for this, but I look forward to trying out the altered ratio with acraglas. Thanks!

Thanks for the info. Temperature also makes a big difference. Want something to cure faster? Warm it up. I've mixed too much epoxy before, and putting the extra in the freezer will keep it useful for quite a while.

With the varying of cure times by varying the mix ratio, is there any perceptible difference in strength or adhesion? Regards, Bill.

Bill, when you look at the cure times vs strength of commercial products the fast cure 5-15 min 1:1 products are in the 2,400 psi category. The longer set products can be as high as 5,000 psi. I have personally not seen any appreciable difference in strength as long as oil removal from the wood is well done. The quicker set tends to be a bit more pliable. For grip split repairs I use the long set plus pins/screws. For things like repairing a split in a Browning Auto 5 forend I will use a quicker set. Especially if the the piece is split off and I can work epoxy into both pieces with a brush. Sometimes I will wet both halves with acetone just before applying the epoxy to make sure I get get good penetration.

Bob

quote:

Originally posted by Bill Leeper:
With the varying of cure times by varying the mix ratio, is there any perceptible difference in strength or adhesion? Regards, Bill.

Very helpful. I didn't know that. Thanks

Thanks, Bob. That is very useful.