Vacuum casting attempt

[Jammer]

OK, how the heck are you supposed to completely mix, pour and shake out the bubbles before the POP sets up? It didn't even give me 7 minutes from when I started adding water and it set up. 50/50 sand plaster of paris mix. I tried to stir it quickly without getting in much air. Is it better to add water to the dry mix or dry to the water?
I'm going to go ahead and try it, but I think I'll have to start over. I'm sure there are lots of bubbles.

[Rasper]

I have found that the sand speeds up the setting of the plaster. To eliminate air bubbles, just before I brush on the first coats of investment mix, I brush down my waxes with a mixture of propylene glycol and water. That's the stuff you put in dishwashers to eliminate water spots on your glassware. Ethylene glycol works as well. I have found that this eliminates bubbles completely.

I use citric acid as a retarder in these brush-on coats. I had to experiment to get the amount right. Too much and the plaster never sets up. At least in my lifetime.

I pre-measure the dry ingredients into buckets before investing. I measure the water into the mixing bucket and pour in the plaster. Then I mix that with this thing I made, chucked in a heavy electric drill.



Then I add the sand as I keep mixing.

I pour this into the sheet metal cylinder while the last brush-on coat is still wet, assuring a bond. If the brush-on coats are at least 1/4 inch thick bonding is not critical, but if they are thinner they will crack and metal will get behind them. Scabbing it is called.

I mix the hell out of the pour-in investment. I don't care about air bubbles in that.

Richard

[Jammer]

I poured the invest in the small one, no problem. I see what your saying, when I did the larger one, I mixed the sand and plaster and let it set for a while. I made sure everything was ready before mixing. The sand was dry but I'm sure it had some moister in it.
So, you mix a small amount to brush on and then mix up the large amount to fill the mold?
It set up hard so I know I can't save the waxes, may go ahead and pour them to see what else might be a problem. Now that I have the program figured out, I can cut out another pattern fairly quickly. I just have wax shavings all over the garage.
I have found a nice tool to join the wax pieces together. Kind of a wire with a small ball on the end. I would like to find one with a larger ball. I was also using a glass stir rod with a round end but after heating it a few times the tip would break off.

[dallen]

cheap pencil soldering iron, or they sell cordless wax tools that I've seen in some peoples videos

https://pmcsupplies.com/max-wax-pen.htm ... oCAJ3w_wcB

[Rasper]

I use what Dave said. I use two, one connected to a wall switch dimmer so I can regulate the heat. I threw the removable soldering tips in the trash and hammered some useful tips out of copper wire.

Yes, I make a slightly different mix for the brush-on coats. It has more % of plaster and I use sifted brick dust instead of sand. Sifted sand would be fine.
I use 1/3 plaster in the pour-on mix.

The trick is to have everything ready so there is no delay at all. I brush on the brush-on coats and I have about ten minutes (because of the citric acid retarder) to get the investment poured.

If you don't want to, or cannot, brush on the investment, the propylene glycol should eliminate the air bubble problem anyway. The difference is amazing. When I first used to brush on investment I had to scrub it onto the wax to get rid of the bubbles. With the propylene glycol, it just flows on.

Richard

[Jammer]

Hey, we're back online.

Working on some other projects right now, winterizing and such.

[Rasper]

Now the AA forum is down, and Lionel's page as well.

Richard

[bunyip]

Jerry, pour the dry ingrediants into the water; you don't end up with dry lumps & minnimises air bubbles. Paint hydrogen peroxide "peroxide" onto you'r wax model & let dry before investing to reduce bubbles forming then "tap" cylinder rapidly whilst still fluid but not hard enough to dislodge the wax. Finally, I use a great little tool I bought from FindingKing on Ebay; it's called "super max wax"& is larger but like a pen & uses 2 AA battery's & has a tip a bit like pyogrophy wood burners. Cheers Trev.

[Jammer]

Now the AA forum is down, and Lionel's page as well.

Richard

The Russians are hacking us for all our casting secrets.

Thanks Trev, I found out about the tapping too much a while back. My wax was floating on top of the plaster. I wonder what the peroxide does? I already got some dishwashing spot free stuff.

[Rasper]

I would never dare tap on most of my investments. Their nature generally puts them out on the very edges of disastrous collapse as it is, especially after I add the weight of the brushed on investment.