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Epoxy Curing Help ?????

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Forum topic by DocSavage45 posted 02-27-2020 12:34 AM 551 views 0 times favorited 27 replies Add to Favorites Watch
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DocSavage45

8912 posts in 3522 days


02-27-2020 12:34 AM

Topic tags/keywords: finishing functional artbox

Lj’s need some assistance.

Might have screwed up but not sure.

Making a art box that will also be a functional soap box for a customer. Per Shipwright”s suggestion (Paul) I purchased some gloss bar top epoxy. Read instructions carefully . Mixed and applied two coats. The second is called a flood coat to the inside of the box top, the walls and interior of the box, and the underside to insure no leaks.

Been cold and epoxy is supposed to be in 70’s (low end) to cure.

Kept the shop at 75 degrees (MN) for at least 6 hours after the flood coat. Then dropped temp down to 60 degrees. At least 24 hours later…the inside of the box feels smooth, the lid is still tacky, and the underside somewhat. Not tacky in all applied sides.

Lot of time in this box routed in a tree and sculpted vent holes to blend.

Checked one YouTube video and the suggestion was to scrape it off! Pine box with walnut accent and splines.

Looking for a less intensive fix and /or advice on epoxy application. ( did find out that the thicker the flood coat the better it will cure. )

All help and positive recommendations is appreciated!

Thanks!

-- Cau Haus Designs, Thomas J. Tieffenbacher


27 replies so far

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shipwright

8496 posts in 3478 days


#1 posted 02-27-2020 12:40 AM

Don’t go scraping anything just yet. Get it in where it’s warm and give it more time. If you mixed it accurately and well enough it will cure. Six hours in good temp really isn’t enough for that stuff. ColdCure, yes but not bartop epoxy.. It’s a quite slow cure to give it time to self level.
Whatever you do, resist the urge to add more hardener!

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

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DocSavage45

8912 posts in 3522 days


#2 posted 02-27-2020 12:53 AM

Paul,

Reading my mind? There is a second flood and fairly well insulated . Always 5 degrees hotter. Moved the box to some shelves upstairs.

Would a heat gun be of any use?

-- Cau Haus Designs, Thomas J. Tieffenbacher

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Rich

5367 posts in 1269 days


#3 posted 02-27-2020 01:07 AM

If you are dealing with some unmixed resin and/or hardener, you can wipe it with acetone to get back down to the cured epoxy.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Greg the Cajun Wood Artist's profile

Greg the Cajun Wood Artist

509 posts in 1622 days


#4 posted 02-27-2020 01:20 AM

Hey Tom… When I have used epoxy resin I always let it cure for 2 days. Temperature plays an important part as much as stirring and mixing the two parts together for 7-8 minutes. If not mixed thoroughly enough it will not dry correctly.

-- Wood for projects is like a good Fart..."better when you cut it yourself" Don't take yourself so seriously. No one else does

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DocSavage45

8912 posts in 3522 days


#5 posted 02-27-2020 01:24 AM

Thanks Greg,

I followed the explicit directions regarding mixing. Hoping that moving it to the upper level where it’s consistently warmer will aid in curing. Hoping I got proportioned accurate. Measured by volume.

-- Cau Haus Designs, Thomas J. Tieffenbacher

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DocSavage45

8912 posts in 3522 days


#6 posted 02-27-2020 01:25 AM

Rich,

Hoping I mixed it well, and I will try the acetone if all else fails.
Thanks!

-- Cau Haus Designs, Thomas J. Tieffenbacher

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Rich

5367 posts in 1269 days


#7 posted 02-27-2020 01:28 AM


Hoping I mixed it well, and I will try the acetone if all else fails.
Thanks!

- DocSavage45

I’m sure you did. It’s probably just going to be a matter of time to let it fully cure.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View MrUnix's profile

MrUnix

7838 posts in 2879 days


#8 posted 02-27-2020 01:33 AM

Yup – give it more heat. Unless you did a really horrible job at mixing, if some parts cured, then the others will also cure eventually. Generally, the thicker areas will cure faster due to the exothermic/endothermic nature of epoxy – thicker stuff heats up more, causing it to cure faster. Dropping the temp just slowed things down, and more so for the thinner areas.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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CaptainKlutz

2701 posts in 2174 days


#9 posted 02-27-2020 02:15 AM

+1 move to inside location above 70° asap.
Keep it above 70° for at 2+ weeks. preferably 4 weeks.

When epoxy requires temp above 70° for cure, it is a requirement and not a recommendation.

This means keeping it above 70° for the entire 7-30 days required to get a full cure. There is no way to shortcut the process. Except using a cure oven set to 110°-130° (and no higher). If the temp is too high is just as bad as too cold. The result is either uncured top surface, or latent internal stress that causes crazing when cooled.

The root of the issue with any epoxy that requires a 70° min cure temp is can end up uncured top skin. The top most layer will remain tacky forever. What happens is low temp allowed the volatile components of the curative to evaporate before available heat was able to finish reacting the top surface. Moving the part to a cool temp before full cure, can result in this phenomenon.

My recommendation is patience and keep it warm for 3-4 weeks.
Once epoxy sets, it takes very long time for remaining not-reacted curative to migrate to top surface and complete cure.

As others have stated, there is recommended fix, but it is a severe remedy that should only be used if not cured after 4+ weeks at required temp:
- Flood surface with acetone to gently wash away left over uncured tacky resin. Don’t run it out as you can leave scratches or embed foreign materials in epoxy.
- Let solvent dry several hours, maybe 24 hours if less than 75°.
- Recoat with thin layer of new epoxy and keep it above cure temp for several weeks.

Hope this helps.
As always YMMV

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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DocSavage45

8912 posts in 3522 days


#10 posted 02-27-2020 03:20 AM

MR. Unix and Captinklutz,

Probably won’t do anymore MN winter Epoxy applications. Can increase temp so second floor is warmer. But my house isn’t even able to maintain 70 degrees as its a big old Victorian.

It’s in the shop and I can push the temp up, but not sure if it will be for 2 weeks.

Woulda shoulda coulda.

Thanks!

-- Cau Haus Designs, Thomas J. Tieffenbacher

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shipwright

8496 posts in 3478 days


#11 posted 02-27-2020 03:55 AM

https://www.systemthree.com/products/cold-cure-cold-weather-epoxy

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

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DocSavage45

8912 posts in 3522 days


#12 posted 02-27-2020 07:01 AM

Paul,

Have you used this. Checked amazon, Got some very negative reviews.

-- Cau Haus Designs, Thomas J. Tieffenbacher

View CaptainKlutz's profile (online now)

CaptainKlutz

2701 posts in 2174 days


#13 posted 02-27-2020 10:03 AM

Think outside the ‘box’. Make a temporary oven !!!

Buy/make a card board box big enough to hold the project, with 12 – 20” of extra head space. Punch holes in top to hold cheap reflector clamp lights . Use regular or reflector type 75W bulb, of old school incandescent type (not LED). The hood of lamp fixture unscrews from the base, so holes only need to be 1.5” to hold the back of reflector in position. Place project in box, turn on light(s). Box interior temp will be much warmer than ambient, temp difference is only limited by insulation value of walls. Top of project will be even warmer due infrared output from incandescent bulb. Use 1 light for ~9-10 sq ft of top surface. If you need more heat in very large box, use 125W heat lamps.
When done, the box folds up and stores nicely for next time.

In a past life used to build composite aircraft structures at home. Built a plywood box as semi-permanent epoxy curing oven. Had to move box from basement to un-heated garage, and added 1” foil covered foam insulation on inside, and box got so hot I had to install temperature controller (like this one) to cycle the lights or the temp was over 150°.

When I needed a larger box for big project, used 1” foil back foam and construction adhesive to hold it together (similar to this random WWW link). Ugly foam box? Yes, but it works really well. Even here in Arizona, the winter low temp is 30-40°F in unheated garage and need a cure oven for epoxy projects.

BTW – If you only need to cure the top of project, can mount clamp lights with heat lamp bulbs to an overhead 2×4 beam, and keep the top surface warm without a box. That is how I cured bar table tops with embedded bottle caps a few decades ago living in midwest. :-)

Now you know, Curing epoxy in colder climates always presents challenges. So it’s important to choose one with cure requirements you can maintain. But using epoxy is always a trade off between properties, and processing parameters. Challenge with some ultra low temp systems is they use faster reacting curatives, which limits mix volume and max cure section thickness without stress. IME – it is better to select the right epoxy for the job, and use an oven to cure; then deal with trade off presented by cold cure epoxy.

For example: the System 3 posted above uses Benzyl alcohol as reactive diluent for lower viscosity, and a combo of fast/slow cure amines to set cure rate. This diluent/curative ‘package’ will have higher elongation, and have softer surface than systems that require higher cure temp. This would not be my choice for any durable bar table top finish. But some folks might think it’s perfect in a cozy living room.

Epoxy is very complex subject. Don’t feel bad about what has happened. It can be fixed.

Last but not least: #IAMAKLUTZ with many years of professional polymer/adhesives background, but still not a expert. So, YMMV :-)

Hope this helps.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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doubleDD

9212 posts in 2723 days


#14 posted 02-27-2020 02:27 PM

Plus +++10 for the cardboard box. On my first two epoxy projects which I didn’t really know what to expect I had a small electric heater going to bring up the temperature. It would seem like sometimes the pour was hardening quickly and sometimes not. Knowing that I was mixing correctly I blamed it on the temperature. I taped a cardboard box around the project and kept one side open for the heat to enter from the heater that was 5 feet away. This solved my problem and also helped keep out floating debris from settling on each coat. Just my 2 cents worth.

-- Dave, Downers Grove, Il. -------- When you run out of ideas, start building your dreams.

View shipwright's profile

shipwright

8496 posts in 3478 days


#15 posted 02-27-2020 03:42 PM



Paul,

Have you used this. Checked amazon, Got some very negative reviews.

- DocSavage45

Only for thirty years of building boats of all sizes in all weather conditions. I never read amazon reviews.
I did, however have the honour of knowing Jim Peters, the brilliant chemist who designed ColdCure and many other specialty epoxies. He was the founder of Industrial Formulators of Canada, later absorbed by System Three.
I wasn’t specifically recommending it for your project but it would certainly work. If this were a bartop, it would not have the self levelling qualities you would want but from my experience I don’t think you would have any hardness issues.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

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