Casting with vacuum and pressure

**dai sensei** · 24th February 2016, 06:15 PM

I often have stuff to be cast, but with a high probability of getting trapped air bubbles that the pressure will not get rid of, but the items being cast do not contain air . In these cases I use Clear Casting Epoxy that gives me a long set-up time and use vacuum initially and then when I think the bubbles are gone transfer to the pressure pot.

Here's a WIP cast I did of resin chips, all sizes from 1-15mm I had in an old chip tube dia 72mm x 240mm long, to be cast in black resin for pepper grinder.
chips1.jpg

I started off attaching some more tube, as the bubbles from the vacuum raise the level of resin considerably, then taped up the joint and lower tube with duct tape in case it leaked (but actually didn't).
chips2.jpg

Then placed in the vacuum chamber whilst in a sink with iced water (hot weather plus extends set-up time) for ~1 minute after full vacuum achieved.
chips in vac.jpg

Then into the pressure pot overnight to set.
chips in pres.jpg

Next the chip tube was turned off to show the bubble free blank.
chips cast.jpg

Also shown is a 50x50x240mm cast of mini pines I cast in clear that often gets air trapped done a similar way (with a silicon mold).
mini cone cast.jpg

And as usual I mixed up too much black resin. But as usual I have spare molds ready to go for casting. So cast up a 3 pen blank block ~65x25x140 of coloured pencils (cast sideways)
pencil cast.jpg

Still more left, so cast up some Red Ash I had with a decent hole. As usual though I ran out of black resin, so mixed up another 50mls of flouro green dyed resin to top up the mold. It will end up as pen blanks, knife scales or something else, block is ~65x25x140
red ash1.jpg red ash2.jpg

Cheers

**Simplicity** · 24th February 2016, 07:50 PM

Thanks Neil,
Never done any casting.
But have always wanted to.
One day I hope
love the red ash one
Sorry I don't have any thing else to add
Matt

**Gabriel** · 24th February 2016, 08:52 PM

Hey Neil,
Looking great!!!
What sort of casting resin do you use? Lately I have been trying poly resin for waste wood pen blanks, but when I turn down to the final size I seem to always get catches where the burl meets the resin (even using a freshly sharpened skew!!) So I have cone to the conclusion that I need to try a different resin.

I purchased some diggers clear casing resin from the green shed but was reasonably expensive for a small quantity. As I would be buying 4+ liters, it would be quite the drain on the bank account so I was wondering if you knew any other suppliers?

The poly resin I have was from a mob in springvale (Bob, ogb, got me onto them - possibly via you) which I will keep gor the solid resin pen blanks I think.

I can't wait to see how your latest castings look once finished....

Cheers
Gab

**Ironwood** · 24th February 2016, 09:09 PM

Looking good Neil. Excellent use of your offcuts. How do you find the epoxy turns compared to PR ?

**dai sensei** · 24th February 2016, 11:19 PM

Originally Posted by Gabriel

Hey Neil,
Looking great!!!
What sort of casting resin do you use? Lately I have been trying poly resin for waste wood pen blanks, but when I turn down to the final size I seem to always get catches where the burl meets the resin (even using a freshly sharpened skew!!) So I have cone to the conclusion that I need to try a different resin.

I purchased some diggers clear casing resin from the green shed but was reasonably expensive for a small quantity. As I would be buying 4+ liters, it would be quite the drain on the bank account so I was wondering if you knew any other suppliers?

The poly resin I have was from a mob in springvale (Bob, ogb, got me onto them - possibly via you) which I will keep gor the solid resin pen blanks I think.

I can't wait to see how your latest castings look once finished....

Cheers
Gab

I am using Megapoxy HX, check out the Megapoxy website for a dealer near you. It is more expensive than PR but certainly cheaper than PR at Bunnies. I get it at ~$16/L buying 20L at a time.

PR is fine for casting, and I have used heaps, but your timber (or whatever you are casting) has to be completely dry (not OMC but 0% moisture that can only be achieved using an oven over time at >120C - OMC to 0% usually takes ~24hrs or more). Try your local Nuplex store for much much cheaper PR than Bunnies, a 4L tin costs me ~$9/L

Originally Posted by Ironwood

Looking good Neil. Excellent use of your offcuts. How do you find the epoxy turns compared to PR ?

Better than PR, less chipping/fracturing, definitely less brittle but harder on the tools I find. Much better adhesion with virtually no shrinkage and does not react to moisture like PR and Aluminite. Has a set-up time usually 1hr or more and full cure after >24hrs.

**Steve Lowe** · 31st March 2016, 09:21 PM

Very nice Neil, you know your stuff I wish I could show you my feeble attemped at useing my vacumme chamber but so far all I have done is create a hot mess

**MarcelloB** · 20th April 2016, 02:06 PM

Thanks for the info. I am having trouble finding the Megapoxy HX on their website. Have they changed the name of it?

one question though, what are you using to dye your resin?

thnaks,

**dai sensei** · 20th April 2016, 03:39 PM

Originally Posted by MarcelloB

Thanks for the info. I am having trouble finding the Megapoxy HX on their website. Have they changed the name of it?

one question though, what are you using to dye your resin?

thnaks,

It's not on their website, not sure why, but when you ring up it's available.

I'm finding all the pigments and translucent dyes (from Barnes/Adelaide Casting Supplies etc) I normally use on PR are working with the epoxy, but I do experiment with small bits first. Pearlex and all of the powdered forms are also ok.

**Phily** · 22nd April 2016, 08:35 PM

Thanks Neil, very useful information. Ref the curing of Epoxy, do you oven cure your final pieces? Cheers Phil

**dai sensei** · 22nd April 2016, 09:33 PM

Originally Posted by Phily

..... curing of Epoxy, do you oven cure your final pieces? Cheers Phil

No need, as long as the proportions are correct, comes out perfect each time. I leave it in the pressure pot for 24hrs and then leave it for another week before turning.

**dai sensei** · 22nd April 2016, 09:49 PM

Originally Posted by Steve Lowe

Very nice Neil, you know your stuff I wish I could show you my feeble attemped at useing my vacumme chamber but so far all I have done is create a hot mess

Vacuum casting is ONLY for long set-up time resins like epoxy. Even then, it is best with only casting things that have no air (timber does), plus you should still use pressure to finish off.

**Phily** · 24th April 2016, 11:08 AM

Neil, is this from experience or just a preference? The reason for asking is that I've been curing the epoxy for just a few hours before turning it. The logic being that the resin still has a Bit of softness in it and so is smoother to cut. I then leave it for a few days before final sanding & polishing. Not suggesting that this is the correct/best approach - self taught. Your thoughts/advice appreciated. Cheers Phil

**dai sensei** · 24th April 2016, 08:14 PM

Originally Posted by Phily

Neil, is this from experience or just a preference? The reason for asking is that I've been curing the epoxy for just a few hours before turning it. The logic being that the resin still has a Bit of softness in it and so is smoother to cut. I then leave it for a few days before final sanding & polishing. Not suggesting that this is the correct/best approach - self taught. Your thoughts/advice appreciated. Cheers Phil

From experience Phil, I've never had to post cure, but keep in mind it is warmer here than down your way and I do leave it in the pot for 24 hrs. I then leave it for a week as I find the epoxy is too soft and can deform too much whilst turning (ie it is still too rubbery).

Are you saying you post cure before turning, to make it softer?

Or are you saying you post cure, to cure it faster, but turn it before it gets too hard?

If you turn it while it is softer (or more rubbery) it's probably fine as long as you don't go too thin. I have had issues with pen blanks getting too soft and peeling when they were "too young"

**Phily** · 24th April 2016, 09:16 PM

The process I have been following is to turn as soon as the resin is hard enough (within 24hrs), then leave it for several days before finishing. Note that most of my castings are quite large so there is a fair bit of resultant heat that helps promote curing. To date I haven't oven cured any of my pieces at any stage (despite the cooler climate here) even though the manufacturers suggest it should be done. I'm trying to work out if oven curing is neccessary/worth the hassle? Cheers Phil

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