West Systems Epoxy and Schweppervescence

[RedShirtGuy]

When mixing up common West Systems epoxy at work (one even dose via pump bottles) I always get tiny little bubbles appearing in the mix container (a small tunafish tin). These bubbles then obviously end up in the work piece, and while some amalgamate into bigger surface bubbles that can be popped before curing, there always seems to be a little bit of "fizz" left behind in the cavity (ie: small holes like bird's eyes and/or bigger "tears").

Am I expecting too much wanting a completely solid mix, or am I doing something wrong?

I've tried changing the way I mix with smaller/bigger stirring sticks and by stirring less vigorously but I can't for the life of me stop "introducing" these little bubbles at the mixing stage.

The teeny bubbles don't stand out *too* much when fully cured, and I know that customers haven't seen them, but I know the blighters are there and it's messing with my OCD :q

[FenceFurniture]

Did someone once say advertising doesn't work? You even got the complex spelling spot on!

[RedShirtGuy]

Lol...I admit, I had to Google it first...remember...OCD :q

[Prle77]

hi reshirtguy..
the bubbles are also caused by chemical reaction during the process of hardening...
As you will see when epoxy cures it emits heat.. as well as some gases...
when using some epoxies you can pop bubbles by going quickly and lightly with the flame torch over them...
I haven't tried that on the western system though.. i guess next time someone uses western system, can try on a bit of excess and advise whether the flame torch works on bubble popping...

Otherwise.. another technique is to pour it a bit thin giving more time for bubbles to surface... also doing it in multiple goes so it is not too deep....
I've used it few times to fill knot holes and ended up with minimum to none of the bubbles captured by pouring it while it is still very runny...
and then spend extended time continuously popping surface bubbles (lets say I've spent about an hour popping bubbles)
Alen

[FenceFurniture]

heh heh, Shweps don't care if you're OCD, can't spell, or both and perhaps more, just keep drinking....

Now what's the bet that the next time you're in the supermarket or servo looking for a drink.........c'mon, you owe them at least one. :D

[Master Splinter]

Vacuum degas if you have the equipment. If not, try pouring it out from further up (like 200mm) in a thinner stream.

[pjt]

Vacuum degas if you have the equipment. If not, try pouring it out from further up (like 200mm) in a thinner stream.
Would you degas the epoxy in the mix container or after it was poured into the hole?


Pete

[62woollybugger]

In a previous job we used to work with various types of epoxies, building military equipment. After mixing they would always be put in a vacuum chamber. We would pull a vacuum & the epoxy would turn to foam as the air came out. Quite often we would have to pull a vacuum & release it several times to collapse the foam to get all the air out.
One other thing we learnt, the hard way, is to keep any uncured silicons well away, as they can migrate through the air & can effect the strength & bonding of other epoxies & glues. After someone, who shall remain nameless :innocent:, put a 2 part silicon mix in the vacuum chamber in one of the critical epoxy process areas, all silicon use was confined to one room in a building at the far end of the site & that room & everything in it had to be scrubbed with solvents to remove the silicon residue.

[Master Splinter]

In the mix container. Combine, mix, degas, use.

[RedShirtGuy]

Thanks folks. A few ideas to try :2tsup:

Most of the time I'm only filling little things like cracked knots or bird's eye and have been pressing the mix into the gap with a spatula to make sure it's in deep and leaving a small mound to sand off later. Any teeny little bubbles in those situations don't bother me *too* much, but it's the bigger tears and deep/wide cavities that have been bugging me (although they still look good enough to send out).

A vaccuum press is a bit too fancy for the amount of work we do with epoxy, but I'll give the thinner pouring and a bit of blowtorching a spin next time and see how it goes.

Ta muchly :)

[steamjunkprops]

The two tricks I've learnt are heat gun/blowtorch to warm up and thin the epoxy.
And the other is spraying to epoxy surface with mold release. This breaks the surface tension allowing any bubbles to pop.

[Robson Valley]

As 62woolybugger describes, air gets into the epoxy from the original components
and from the stirring/mixing process. Degassing several times in a vacuum chamber seems to
be the sole cure for it.

I don't agree that gasses are released during the cross linking polymerization process.
Otherwise I should have expected to see all of my biological research specimens
ruined. Not the case. 3+ years of as much as 30,000X in an electron microscope
showed no bubbles.

[FenceFurniture]

As it happens I had some cracks and holes to fill with epoxy today in some recycled timber, so I thought I'd trying the vacuum process. I happen to have an Orved v12 Vac-Pack machine (can't sell the damn thing - maybe I don't want to now :D). Gave the mix 6-8 good long runs in the vac and it certainly removed most of the bubbles - just a few very small ones that probably won't be noticeable.

Thanks to Master Splinter (again) for the tip.

After the first second or so of the vac process I could see the chamber get filled with a smoky vapour - not dense, but certainly easily visible. What the hell could that be I wonder?

I didn't think to do the vac with the first batch today, and so i hit the epoxy (already in the holes) with a small butane torch. It looks to have made the bubbles come up above the timber line so they can be sanded out, but tomorrow will reveal the truth.

If the epoxy is going white around the edges under the butane torch is that a sign of too much heat?

[Master Splinter]

If the epoxy is going white around the edges under the butane torch is that a sign of too much heat?

It can be - but it can also be water vapour condensing out of the flame envelope onto the colder epoxy.

But the reaction can kinda' get away from you, as the hot epoxy reacts faster when warmed and can then exotherm, increasing its temperature even more.

(Rule of thumb is that a chemical reaction doubles in speed for every 10 degree increase in temperature).

[FenceFurniture]

Cheers MS. As I thought, the bubbles have risen to above the timber line, and so were virtually all gone after I sanded back.

Interestingly, the epoxy mixed with Saw dust was significantly harder after the same time than the clear epoxy with no dust which was still quite sticky.

[soundman]

I know this thread has a bit of age to it now. but here are some things I have learned.

I use disposable plastic measuring cups to mix my epoxy and have gone off pumps, because that can airate the material among other issues
The measuring cups in conjunction with either icecream sticks or tounge dipressors allow me to scrape the sides and work in a more folding motion than sturing.....but ya still get bubbles.

( let the epoxy dry in the cups and it will come out by flexing the cup..reuse many times.)

using slower hardener allows time for the bubbles to come up.

realise that some of the bubbles will be air comming out of the wood, displaced by the incomming epoxy..if ya filling knots and cracks those bubbles can be quite large.

If ya using it as a surface coating.....you may get heaps of bubbles comming out of the surface.

one trick with both epoxy and clear finishes is to put the workpiece in the sun ( or under a lamp) and get it good and warm.....bring it into the cool and get the epoxy on it straight away.....the warm surface will help the epoxy flow and the air in the wood will begin to contract as it cools.

I've not had great sucess with heating the epoxy, as it tends to go off faster.....heating the job is better.

Oh and watch your temperature and humidity..extreemes of either are not helpfull.

If you have played with the clear pouring epoxies, they can be realy narky about temp & humidity.

If using a torch to raise bubbles it not the heat you are looking for..its the co2......a drinking straw works just as well.......just take a deep breath away from the epoxy...smooth even blow on the surface raises the bubbles...not sure why it works but it does.

On those deep cracks, two applications can be the go.....the first one gets in and seals up the voids and the second does the filling.



cheers