molding epoxy bubbles

[Rich Burnoski]

How do keep bubbles out of epoxy when your mixing it for molding? Richard

[Daryl Perkins]

What are you molding Rich? Bubbles in the resin are not a problem unless you are using it as a surface coat for a mold.

D

[Goinav8n]

Richard

You can take the resin and put it in a jar and vaccum the bubbles out. It then brushes on easier

Jeff

[Rich Burnoski]

I should clarify Im mixing MGS 2 part with a short working time of 15 minute pot life.

When I pour the epoxy in a mixing cup, both the resin and hardener have no bubbles before I start mixing. The resin is a little thicker compared to the hardener.
I start mixing and zillions of little bubbles appear.
Maybe Im over mixing the epoxy mix in the cup?? Its hard to know exactly when to stop mixing or when your over mixing.

And or my basement is a little cold these Chicago wintry days and the resin should be heated a bit before I mix the two. ??

Or are bubbles normal in the cup and I should accept them?

Any thoughts you epoxy experts? Richard

[Daryl Perkins]

Rich,

The parts I made for you today started out with bubbles in the resin after mixing.... you won't find any in the parts.

D

[prodjx]

If your mixing in a cup with a tongue depressor that happen's almost all the time, even when I use a credit type card and mix on a flat plate there are still air bouble's, and I know the vacuume does work. Are you doing a contact lay-up or are you bagging it? BTW I too like using MGS resin, my 1.5gal. kit last's forever it seem's.

[Mark Miller]

Try mixing in the cup and then pouring into another cup. The pour will pop most of the bubbles.

Mark

[Jim Frahm]

Try mixing in the cup and then pouring into another cup. The pour will pop most of the bubbles.

Mark

Mark nailed it, but you want to do a long slow pour; how's your aim?

Jim

[Rich Burnoski]

Ive been mixing the MGS with an electric drill set at slow to medium speed and an attachment paddle made out of a 3/4" metal wood router bit with the point broken removed.

Double pour-
Neat idea,,,, a long slow pour into a prep cup. That might be a good move when doing contact work. Ill have to try it.
I do understand that vacuuming projects would make the bubbles go bye bye!

Thanks guys for the notes. Richard

[prodjx]

The technique at Grumman's Advanced Composite's facility was to pour epoxy casting C-301 from 6ft up, through a strainer with a heat gun trained on it for good measure. It sound's bizarre but it worked. I on the other hand was doing wet lay-up's using a saber saw with a paint brush attached to it so I didn't have to hand stipple the lay-up buy hand. I got lucky, that idea worked really well, it used 2/3rd's less resin and was 3 time's stronger according to some engineer's, it also made the tool ring after it was cured.

[Speedo125]

Having recently become interested in molding, I've been doing some online research. As Jeff indicated, the vacuum process is the industry standard for getting the bubbles out of the mix. They place the container of mixed resin into a slightly larger container, seal it, and pull a vacuum. Apparently this causes the bubbles to expand and rise to the surface where they burst. I haven't tried it yet, but I would imagine a wing bagging setup would do for pulling the vacuum.
Thom

[prodjx]

Our vaccume chamber had a very thick lic of lexan so we could make the process stop if the resin was getting too close to it's container top, it was interresting to watch.

[nuevo]

here is a neat video demonstrating vacuum degassing

http://www.freemansupply.com/video/preparing/vacdegas.htm

[SmokinJoe101]

If you apply heat the bubbles go away.

sj

[lincoln]

I've done the vacuum thing. It works pretty well on the urethane we were mixing, but I think it requires a really good vacuum to work really well. Like, 30 inches of mercury. Keep in mind that the bubbles expand inversely proportional to the pressure. I.e. if you pull 30 inches of mercury and the atmosphere is 31, the bubbles will be 31 times as big, which makes them float up and pop quickly. Don't put on all the vacuum at once, and use a container that leaves a lot of space above the epoxy or it will really mess up your bell jar.

I'd like to hear more about this stippling. I've never bothered to do it and I'm not tremendously clear on what it does or what it's for.

[prodjx]

lincoln, I once a fellow tooler hand stippling a tooling lay-up for 8-10hr's and he was exausted my idea on the other hand was doing 2,000 strokes per minute. The black Hexel tooling resin we were usingf at the time would actually turn gray because we were using that much less resin to wet out the glass. My pneumatic stippler would eliminate air boubles and also cause glass fabric to get pushed around steel embedment knurled bushing's that would normally require cutting hole's in the cloth, this saved time. Grumman and I tried to patent the idea but after 2 year's of trying we gave up and I recieved a letter from Grumman's legal dept. saying I could do whatever I wanted to with the Idea so I called up Clint Richey, Burt Rutan's tooling guy and told him about my idea, maybe they used it.