pressure pot - or old pressure cooker

bigegg · Jan 30, 2019

Im still working on my resin casting projects, and I need a pressure pot to force the resin to degass and also to stabilise any organic material I imbed.

most utube videos seem to use a paint pressure pot, which are £100+, even from the 'bay on a 6 week delivery. :rolleyes:

for the stuff I'm casting, a stove top pressure cooker will be big enough, but I'm struggling to get hold of a second hand one locally.

does anyone have an old one they would swap for beer tokens?

or a *cheap* paint pressure pot - the 10l type, not the small ones off a gun!

ta

julianf · Jan 31, 2019

Charity shops often seem to have them?

bigegg · Jan 31, 2019

julianf said:
Charity shops often seem to have them?

not round here

Maker · Jan 31, 2019

You need a vacuum chamber to de-gas don't you? :dontknow:

bigegg · Jan 31, 2019

Maker said:
You need a vacuum chamber to de-gas don't you?

yes.
but for resin, you put it under pressure which shrinks the bubbles - but more importantly, forces the resin into any cavities in the encased items (such as wood pores).

poor choice of words on my part. :ashamed:

julianf · Jan 31, 2019

How much pressure do you need?

Could you use a homebrew barrel thing? The ones for serving rather than brewing - brown things with the little co2 bulb.

Could pump it up with a bike pump (if it is indeed pressure that you need?)

julianf · Jan 31, 2019

I've got a 400ltr pressure vessel, but I think the logistics of lending it to you would be a little too involved....

julianf · Jan 31, 2019

julianf said:
How much pressure do you need?

Could you use a homebrew barrel thing? The ones for serving rather than brewing - brown things with the little co2 bulb.

Could pump it up with a bike pump (if it is indeed pressure that you need?)

Ps always loads of them down at the dump shop.

bigegg · Jan 31, 2019

I need something to hold about 30-50psi.

I don't think plastic homebrew barrels will hold the pressure, OR have a wide enough opening to allow the mould to be put inside.

<edit> apparently 15psi maximum for plastic barrels

bigegg · Jan 31, 2019

julianf said:
Ps always loads of them down at the dump shop.

I've got a couple in the back of the shed, waiting for next crop of apples.

bigegg · Jan 31, 2019

julianf said:
I've got a 400ltr pressure vessel, but I think the logistics of lending it to you would be a little too involved....

lol.
I'll bear it in mind if I decide to cast a life size statue.
:thumbup:

julianf · Jan 31, 2019

Is a soil pipe too small a diameter for you?

I made a receiver for an, umm, trajectory testing device, using a section of soil pipe once. I know they're not pressure rated, but, if I was to say that the reason why the project got scrapped was that the tachometer / maths declared fire arms certificates were needed, then it's clear that they can go up fairly high.

(I can't recall the pressure now, but I think the squash ball was clocked at over 120mph - which on a 20somthing gram ball put it at about the same foot pounds as a Browing pistol... )

bigegg · Jan 31, 2019

too many horror stories for plastic pipe under pressure.

knighty · Jan 31, 2019

asking because I'm curious.... does a vacuum not work as well/better for casting?

bigegg · Jan 31, 2019

knighty said:
asking because I'm curious.... does a vacuum not work as well/better for casting?

depends on the casting.

if youre making a homogenous casting in resin then its about the same - although vacuum does seem to produce foaming on the top surface

casting plaster or concrete, vacuum is better.

if youre making micarta, or embedding or otherwise stabilising organic matter in resin, then pressure works better.

Lazurus · Jan 31, 2019

If you purchase a Chinese paint pressure pot it is easy to adapt, I did mine for around £60 including the pot, can also double up as a vacuum chamber if you get a 10mm plus acrylic lid etc. Been using it for a couple of years now with great success. Lots of vids on youtube.