Variations in Epoxy From Same Manufacturer?

I have been using System Three General Purpose epoxy for any wood coating, bogging and for coves for bulkheads. It's softer than the SilverTip laminating resin, so it's perfect for these applications.

Recently, I got some more of the medium hardener in.

The new batch, instead of being purely amber in color, is a purplish amber color. It also went off CRAZY fast compared to the old stuff and ruined a cove joint I was working on today!

At the bottom of the post you can see what the hardeners look like side by side.

Do you think this is of concern, or do you find that epoxy coming from a specific vendor varies from batch to batch?

Add on question: I have a cove joint that's partially lumpy. About 15% of the length of the cove is epoxy that went off too quickly before I could form the cove. The rest is in good shape as I rushed to cove it in. Now what do I do to fix the bad part?

 

Sully,

I had the same experience with some epoxy from Fiberglass Hawaii. One batch of part B was much darker than another of the same stuff. I called them and they told me it was a result of oxidation (IIRC) and would not affect the epoxy. I went ahead and used it and didn't notice a difference. Definitely did not go off faster. Might be worth a call to the folks at System 3 to see whassup.

Mike

 

Darkening with age is normal but this does not change the curing rate. The product is either mislabeled or contaminated with previous product in the fill line.
Best to have it exchanged.

I assume that the bog had not started to gel before it went into the join, then just sand the lumpy section smooth.

 

My wife pointed out that the evenings are 10 deg F warmer than usual and of course, it was 101F (38.3C) at the warmest today.. I think the warmer nights and slightly warmer day may be responsible for the perceived speed of curing. Thanks for the thoughts. I have contacted support just to be safe about the color difference.

 

I would just sand it smooth as AndrewK said.

 

I'm working on my 3rd 5 gallon jug of System III Silvertip in the last 3 months. I'm in New Hampshire, the trend is temperatures are rising.

First 2.5 jug was fast hardener, 2nd 2.5 jug was fast hardener. Well I swear the first 2.5 jug of hardener went off waaaay faster than the 2nd..

The first jug was used in 40's - 50's and the second was used in 50's-70's.

Only thing I can think of is humidity. Up here when it's warm it's usually humid, when it's cold it's dry.

All of the stuff worked fine.

My experience with epoxy is to disregard color, stuff takes on air and changes color pretty easily. In cold temps (ie freezing), it's even common to have it turn white on you, doesn't mean anything (heat it and it goes away, mix it and it heats itself and goes clear).

Jon

 

Thanks for the tip from experience with System Three.

The humidity is starting to increase over winter down here, but the temperatures are just crazy, usually. 101 was the high yesterday.

I used it again today on a cove and this time I was very careful to really spot cool the bulkhead down and make sure to smooth the cove instantly. Came out nice again.

I think the speed was the heat, but the color... well, I have no idea.

 

If you're comparing hardeners, it has to be done in the same temperature and humidity, other wise it's a worthless comparison. At 101, even supper slow is going to kick off pretty quick. If working in these temperatures, you need a special formulation that offers the working time you need. My proprietary super slow will offer about 45 minutes at that temperature, but West System 209 super slow will be kicking long before this and System Three's slow will go off in 15 minutes or less.

 

I'm not sure if epoxy follows a similar curve, but you'll get the idea.

Polyesters are tested and QC'd at 77F for gel time, visc, thix, etc.

For about every 15 degrees you increase the temperature above 77 the gel time is cut in half.

For every 15 degrees below 77 the gel time is about doubled.

This isn't exact and every formula will be slightly different, but it gives at least a guideline of what to expect for a fabricator.

We get flooded with calls every spring asking why we sped up the gel time on products, and then again in the fall asking why we lengthened them.

 

Yep that's right; I think epoxy is something like 18 degrees. I'm not sure if they really stress "gel time" rather just that every 18 degrees down doubles dry time.

Only difference is epoxy can (and usually does), by design, take waaaaay longer, so in some extreme cases it might take days to dry (with no impact on the final product).

Jon

 

It actually is closer to 18 minutes on polyester, but we typically say 15 because it's easier for people to deal with.

 

These thermoset plastic resin systems, all react similarly to temperature differences. Experienced users progress through fast to slow hardeners in the spring and the reverse in the fall.

 

One thing I'm trying to do is stay with medium speed through the summer, if I can, for the bogging and coving epoxy.

The reasoning is that the slow hardener requires post curing, while all others don't.

The Silvertip laminating epoxy doesn't require curing with fast or slow, just the general purpose does.

 

Change of color will be change in Promoting , need to look at batch numbers on the bottles and do some asking . New bottle so do some samples just small quantities but at least you will know the gel time .:idea:
Even working with poly or vinylester resin i take 2 samles a day ,one in the morning and one in the early afternoon . Bottom of a coke can ! waxed is good just pour a little resin in and write the temprature the humidity and the time it took to gel . write it on the sample and when hard put in a place that easy to see them in a while You will build a picture of the effects of temp and humidity have on your resin mix's .
I have samples that have same temp and differant humidity with a 8 minute differance in gel time with poly resin .
Humidity really can slow things down . even at the same temprature

 

You have to use the speed you need for the conditions, not attempt to force medium goo to preform the tasks, much better suited for a slow goo. You'll have repeated issues if you take this approach.