EPOXY SOFT. WHAT THE (*$^$%#*^@

[davebrown]

A curious thing has happened. Last night I laid about 6 ft. of fiberglass tape in epoxy on a plywood seam. The seams were originally fileted with same, and have been dry and cured hard for a good month now. I used my usual ratios (2:1 and 3:1, with two different hardeners, depending on which I wanted to dry faster). I used 2-3 oz. mixes and ran several batches.
The temperature was quite warm last night (Sacramento), and got up to 104 today. The boat is in my garage, which means at 3 today it could have been 110 or hotter inside.
Appr. 26 hrs later, the epoxy is still quite soft. I would liken it to the stiffness of refridgerated butter: you can easily put a thumbnail into it.
Everything I have read suggests a mixing ratio error, yet I mixed a good half dozen pots over the course of the evening. I don't think even my bumbling skills would have resulted in that many batches being off. Further, this is my third boat, and I have never erred on ratios before, using a teaspoon as my ratio guide. Not the most precise, but so far, no problems.

QUESTION: if the ratios are wrong, will it eventually harden, or must I tear it out and reglue? Obviously, time will tell, but I am sure some others have experienced this issue.

Second, could the high heat have either kept it from curing, or softened it during one of the curing stages? In which case, I would think it will harden, eventually...

This is a mystery. Any advice?

And one last comment. It is possible that I confused the two hardeners and mixed them opposite, over the course of the evening.

[JimConlin]

My bet is that the ratios were off. The only remedy is to remove the offending goop, whether by tearing it off, the solvent of your choice (acetone or vinegar) or abrasives.

I once had 120 ft^2 of a strip planked deck/coach roof go wrong this way. Wasn't pleasant.

[warthog5]

Are you using pumps? They have been known to be off.
I never use them.

[NormMessinger]

I fear jim is correct. Time is not your friend. Heat only makes the stuff get hard faster. What brand are you using? Not that that is particularly relevent. I'd run the question past your supplier if you are absotively posolutly sure of the ratios and let them abuse you.

[davebrown]

Thanks for replies. Appears I confused the two bottles then, and I must have reversed the ratios. I was not using a pump, I was using a teaspoon, as I have for 2.75 boats so far.

Vinegar it is.

This would have been the last interior epoxy job.

GRRRR.

I am in a big hurry to finish this one, so I can start the next one.

[Phil Young]

Hurry slowly you'll save time in the long run

[Bob Perkins]

Hi Dave,

Which epoxy system do you use that has a 3:1 ratio?

I've only heard of 2:1 and 5:1 (West System).

just curious..

I'm assuming you know that adding more hardner does not make epoxy get harder faster - it ruins it and you will have a gooey mess.

With most epoxy's you are allowed to be off +- 10% and have everything work ok.

Good Luck,
Bob

[NormMessinger]

A teaspoon? You mixing epoxy or taking medicine? ;)

I know I know. I shouldn't be teasing when I don't know the whole story. Might not be a bad technique for small quantities. But for 3 oz quantities and up the pumps have worked satisfactorily for me. Ya gotta pay attention however and pump into a graduated container, at least every few batches. And pay attention to the resin so you can deal with any crystalization before it jams the little check balls open. It rarely happens but it can.

[JimConlin]

No method of measuring epoxy is completely error-free, but the mustard pumps, when used in the right way, are better than anything else I know of. I've had one off-ratio experience in 15 years. That was when the spacer which limits the stroke of a hardener pump got dislodged.
It's important to make the procedure for pumping a batch routine. I have ingrained in myself the habit of first pumping a squirt of resin, then a squirt of hardener, and as it says on the shampoo bottle, repeat. The resin squirt is always first and i make a point of the following squirt of the hardener before I do anything else 'cept breathe. If I lose count, the quantity may be off, but the ratio is right. No harm.
For larger quantitities, a quart or more, i weigh it. An electronic kitchen scale makes this quick. Put the cup on the scale and zero it, measure a quantity of hardener into a cup and note the weight. Multiply that by 6 (for 5:1 epoxy) and add resin 'til that weight is reached.

[John Bell]

Measuring ratios by weight is best, but check with your supplier for the proper ratio. The density of the resin and the hardeners is not the same.

Consider for example West 105/205:

105 resin has a specific gravity of 1.15
205 hardener has specific gravity of 1.05

If you mix them with volume ratio of 5:1, you wind up with a weight ratio of 5.75:1.05, which reduces to a ratio of 5.48 parts by weight of resin to 1 part by weight of hardener.

If you assume they have the same density and weight them out 5:1 as is, in reality you'll be short on resin compared to what the manufacturer recommends.

[ 08-12-2004, 05:27 PM: Message edited by: John Bell ]

[Bob Perkins]

I've been mixing bigger than 3 pump batches recently. For that - I too use the digital kitchen scale (inside a zip lock bag..)

It is very accurate and I have had no bad mixes.
Using System 3 or MAS makes it much easer that doing 5:1 ratio math.

Take Care,
Bob

[davebrown]

IN answer to the question of which epoxy uses a 3:1, I don't recall the brand name except I bought it through Defender Industries about a year ago or so. I have been measuring by volume--I take exact level teaspoons and make up a small batch, then keep mixing as I go along. This is abit cumbersome, but in the heat we have been having, I kept having larger batches kick off too fast.

[NormMessinger]

Oh, there are better systems for pumping out the correct amount of epoxy than the catsup squirters. Trouble is I never come to that conclusion until AFTER a big job. Up front shelling out something like $150 for an epoxy pump when the mustard blasters will do seems ridiculous. After spending hundreds on a boat, neigh thousands, or thousands for an airplane, $150 seems inconsequential. Another flaw in my personality revealed.

[paul oman]

most of us in the industry measure out epoxy by weight instead of volume. Just need the w/w ratio (different from the vol/vol ratio), a scale, and a calculator.

Actually the ratios off all epoxies are computed by molecular weights in the first place. The volume ratios are just approximations for "outsiders" and the pumps are sort of (not quite) a gimmick with a nice $$ mark-up and a reason to keep you from trying other brands of product.

Still, pilot error happens to everyone.
I've heard that in the days of tall ships it was never the new guys that fell out of the rigging to their deaths, but rather the experineced 'old hands'

I can speak from experience about sloppy mixing and measuring out.......

regards

paul oman
progressive epoxy polymers
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[JimConlin]

Yes, Norm i do have a 'goo grinder' or a 'sticky stuff dispenser' on my list. I wish they'd make one where i could switch between slow and fast hardeners.

Jim

[JimJ]

For small quantities I use a plastic 25ml syringe.

[Corso]

Siringes work well, never off, and are easy to clean to be stored and reused, sampling siringes can be as big as 500 ml, vets can give (or tell where to find) magnum sizes too, with some little modifications pastry siringes work well and cost pratically nothing. If you find the right sizes you can go with one siringe of this and one of that. When it comes on glueing siringes are fast and clean.

[ion barnes]

What is the self life expectations?

[Shalfleet]

I second the syringe idea. My local pharmacy gives them out for free and you can accurately measure down to 1ml with the small ones if you are so inclined. They are easy to keep clean for the most part. BTW, I have kept mixed epoxy in the freezer overnight in a syringe, (inside a ziplock bag to avoid any chance of condensation). This avoids wasting if you mix too much.