Thread: Sawdust

Neil I know you love mixing wood and acrylics, but that's just a bit too over the top I would try turning and see what results you get ,you may be surprised, at the worst you could show only the good sides for sample purposes hehe, cheers ~ John

mate i would try turning one up to see what happens, looks like the wood maybe just on the top

worse case, you loose 5 minutes

i am glad to hear you like the way the moulds work

MIK

Originally Posted by gawdelpus

...I would try turning and see what results you get ,you may be surprised, at the worst you could show only the good sides for sample purposes hehe, cheers ~ John

Possible, but not sure it is worth the effort. I've already madesome new ones to play with

Originally Posted by MBUMIK

.. looks like the wood maybe just on the top

Nah, it's all the way to the middle on most of them

Neil we all now no not to use saw dust I picked up a pot on the weekend. What mods did you do to yours?
David

Originally Posted by dai sensei

instead of pouring some plaster in the bottom like I planned (I had no plaster), I got the bright idea of using sawdust to create the level bed. Placed

Sand might have worked.

I'm sure I had nothing to do with this I only make the stuff

seriously - what a bummer, something else on the not to do list

Originally Posted by dj_pnevans

Neil we all now no not to use saw dust I picked up a pot on the weekend. What mods did you do to yours?
David

I took the old paint extractor shaft out, the one the paint is drawn up from. I added a pressure guage and water trap also.

I have just bought a venturi vacuum pump and vacuum guage. I have designed a pipe system that will allow me to vacuum initially, then swap to pressure, avoiding the trapped air problems I sometimes get (especially on banksia).

Originally Posted by munruben

Sand might have worked.

Nah, probably same result, the air pressure through the small hole in the top blows it around. I will go back to plaster, mixed and poured in base over baking powder, so I can remove it if necessary.

I made up a little stand with an extra piece on the bottom that sits in the round base and keeps the whole lot steady. See my pressure pot thread.

As I now also use conduit I have also put a T piece in the inlet so that the air doesn't go straight down in to the open conduit, which sit in a block that straddles the round base.

What capacity is the dip is the bottom of your pot? Couldn't you just use some excess resin after filling a turning blank?

With a bit of release agent on the bottom first, of course?

I have yet to set up my "pot" so all these ideas are useful ,never thought about a flat bottom ,maybe a simple round cutout plywood support that just slides into the pot .with a couple of finger holes drilled for easy removal ( a false bottom) hehe.

Originally Posted by gawdelpus

,maybe a simple round cutout plywood support that just slides into the pot .with a couple of finger holes drilled for easy removal ( a false bottom) hehe.

That's what I use in my pressure pot. Then I just have to remember to level my rocking
table before I pour I use a piece if 3/8" plywood (rounded on the lathe) with two
finger holes so I can remove it. Works like a charm.

A few things.. if you're going to use vacuum, please do it before you pour. When you
remove the air from the pressure pot, something will want to replace the missing air..
namely: resin. When you suck the air out of the tubes, the resin will replace it.

Best route is to open the containers, put them in the pot and then pull a vacuum for several
minutes. I do this after I warm the bottles in a pan of hot water. This thins out the resin
and then de-gassing with vacuum gets rid of suspended air. Then mix carefully.
But with warm resin, any air bubbles you introduce by mixing will easily rise to the surface
since the resin is much thinner when it is warm. (closer to water consistency)

Careful on the pressure, too.. the silicone is soft and pressure can distort it. That could
also let resin into the tubes. I've had goo luck at 20-25psi (don't know what that is in bars)

From the picture you can see the sawdust sinking in the resin, which is too bad.
Sometimes I'll accidentally drop things on the resin .. so far they've stayed on top
where they got turned off. I was lucky.

Also, Skewchi is right.. if you pour resin (after release) in the bottom, it will make a
perfect fit for your pot. Just make sure your pressure pot is perfectly level first.
And pouring resin into a round bottom doesn't seem to give you the same problem
of shrinkage that a square wall does. When it shrinks in a round bottom, it tends to
follow the shape of the bottom as it shrinks.

Glad you got to try them! Looking good so far..

ps .. release isn't necessary with silicone, but it will help extend the life of the molds..

Ah! So the pressure pot is on the go? Too bad about the sawdust. I think I would have used a little round wire rack I have kicking round the kitchen. (So any chance of those bigger cast banksia blanks? )

Originally Posted by Big Shed

I made up a little stand with an extra piece on the bottom that sits in the round base and keeps the whole lot steady. See my pressure pot thread.

As I now also use conduit I have also put a T piece in the inlet so that the air doesn't go straight down in to the open conduit, which sit in a block that straddles the round base.

I have a similar rack, but it slopes (rocks) too much on the round bottom and the resin spills if not perfectly in the middle.

Good idea with the Tee, I'll see what I can fit in. I've been using a perforated plate on timber spacers over the moulds, but forgot this time

Originally Posted by Skew ChiDAMN!!

What capacity is the dip is the bottom of your pot? Couldn't you just use some excess resin after filling a turning blank?

Tis a bit much for resin, cost wise, hence my suggested use of plaster with sloppy mix

Originally Posted by NewLondon88

Careful on the pressure, too.. the silicone is soft and pressure can distort it. That could
also let resin into the tubes. I've had goo luck at 20-25psi (don't know what that is in bars)

I'm running at 60psi without any trouble with the moulds leaking. I need to bump it up higher so I can use the venturi with the same pressure.

Originally Posted by NewLondon88

A few things.. if you're going to use vacuum, please do it before you pour. When you
remove the air from the pressure pot, something will want to replace the missing air..
namely: resin. When you suck the air out of the tubes, the resin will replace it.

My problems are not so much air bubbles in the resin, the pressure seems to force them out anyway. My problem is entrapped air as you cast, mainly on the banksia, but your point regarding extra resin required is correct.

Originally Posted by tea lady

Ah! So the pressure pot is on the go? Too bad about the sawdust. I think I would have used a little round wire rack I have kicking round the kitchen. (So any chance of those bigger cast banksia blanks? )

The pressure pot has been on the go for a while, it is the vacuum that I was waiting for. Just got my venturi vacuum and vacuum gauge, so now I can finish my set-up and try more banksias

Bugger ! getting too high tech for me hehe, next you will want a "centrifuge"
Cheers John