Test casting

[raspero]

I am doing an ancient Egyptian queen, about 2/3 life size. This is a failed casting. There was still moisture in the investment.



A few weeks ago I cast the front part of her crown.



The vulture head is solid, not hollow. I wanted to test to see how it filled before pouring the entire crown. I have too much work invested in the wax to take chances with it. All of the shrinkage was in the gate, exactly where it should have been.

I put a patina on it.



Now I am preparing to pour the queen again. This time no moisture.

Richard

[Dries]

Some interesting work you busy with Richard, as a matter of interest how long and at what temperature do you do your burnout?
And do you use a gas or electric oven for the burnout?

[raspero]

The queen was invested in a 16 inch diameter (40.6 cm) X 28 inch tall (71 cm) cylinder. I burned it out at 1000 F (538 C) for about 80 hours. It was not enough. I am going to burn her out this time for six days at 900 F.

The little crown piece was invested in a cylinder 12 inches diameter (30.5 cm) and 12 inches tall. I burned it out at 900 F. (482 C) for 48 hours. That was plenty.

There are a lot of conflicting opinions in the sculpture world about burnouts. It seems every book I read says something different. I have found that many, if not most, book writers tend to let other books do a lot of their research, the writers of which let yet other books do their research. It's kind of circular. So I finally found a man who knows what he is talking about. B.P. Fink is a professional. He has poured hundreds of both ceramic shell and plaster investment molds. He much prefers plaster investment. You can find his wisdom on the http://www.artmetal.com/ forum. He burns out at 900 F. for six or seven days. That's a great forum. Not much chit chat, but some real knowledgeable people who are right there when I need them.

Richard

[Dries]

I agree with you Richard any burnout is affected by the size oven etc and I will visit the suggested site. You know what seem to speed up the burnout process for me is to place the mold into the oven about an hour after investing. When the mold is still wet its transfers the heat faster to the core than if the mold is bone dry. I think the type of wax invested will also affect the pour. Thanks again for sharing.

[obseq]

No mold of the wax?
And yes, many differing approaches to burnouts; all seemingly the "right" way to go.
Are you able to perform multiple burnouts on your investment?

[raspero]

No mold of the wax?

Yes, I have a rubber mold for making more waxes, but it's the added details I added to the wax to the hundreds of feathers that I do not want to have to do over again.

Richard

[rika]

Have you got around to finish this piece? love the patina on the vulture.

[raspero]

I did that patina with the simplest of methods as a test. I used vinegar and ammonia. I think I buried it in sawdust and poured the liquids on the sawdust, but I am not positive. But first I darkened it a little with Birchwood-Casey M-24.

This time I cast her in two pieces. I poured her head first.



Then her torso.



Not so perfect a casting as her head, but useable.

Welded up.



And she is coming along.



More to come.

Richard

[cheesepaws]

Wow - gorgeous work.

I have only used ceramic shell, which I know is expensive, but weighed against the time required to burn out sand molds or other investments......sheesh! 80 hours! Six days!!!

I'd never be that patient!

[rika]

Richard, I have to say that I love the original cast's natural "patina", the variations of colour are beautiful and remind me of ancient bronzes. In my opinions this resonates well with the theme as well. Just a little bit of verdigris and done. The polished piece is very nice too, but the other one is captivating.

[raspero]

I think you are right. I am doing a series of Ancient Egyptian inspired pieces and am thinking of casting her head again and doing what you said. The gating adds a certain strangeness to it.

Richard

[raspero]

Rika, Both you and Mantrid have said the same thing about her head "as cast". I have been hanging out with it overnight and what you said has shifted something for me.

"There is a distinct difference between nice and captivating.

Lesson learned. Thank you to both Rika and Mantrid.

Richard

[rika]

Absolutely, there is a difference. And you know it. This is how we learn to act on our instinct. Never stick to the original plan if a beautiful "accident" comes our way. It is rare and we have to run with it. Been there, done that, and it takes nerve and experience to undo all the perfecting, polishing touches that you did on this piece. I applaud you for it because it is a difficult thing to do. Also, the unknown of the future process...because most likely it will be different next time.

[mantrid]

the nose seems different in the polished piece. did you remove alot of metal to get down to perfect metal?
if so it is strange as it has taken away something and added something else. it now looks less natural but at the same time it makes the character look stronger more fitting of a queen.

or maybe its just the polished surface that makes it look different and the application of a patina will change it again

it might be difficult to get back that as cast look. something to try is to heat it with a torch in air, this will oxidise the surface blackening it. then apply carbon powder or something that breaks down to carbon such as sawdust then heat again. copper is less reactive than carbon so carbon will steal the oxygen from the black oxide turning it back to copper and hopefully reproducing those coppery hues (different amounts of carbon giving a slightly different colour). ive never tried this technique its just a hunch based on my understanding of the chemistry. it would probably involve some trial and error to get it right, or it might just not work

[raspero]

the nose seems different in the polished piece.

All I did to her head was to cut off some little bumps with a chisel and sand it a little. Shiny adds complexity to a surface that changes its appearance a lot. I learned that back in the 1950's when I was a high school kid into cars. We used to paint our cars with primer and leave them like that. I began to notice how cars looked different with a primer finish as opposed to how they looked when shiny. Some looked better with primer and some not as good.

Richard

[Nelson]

Originally Posted by raspero

All I did to her head was to cut off some little bumps with a chisel and sand it a little. Shiny adds complexity to a surface that changes its appearance a lot. I learned that back in the 1950's when I was a high school kid into cars. We used to paint our cars with primer and leave them like that. I began to notice how cars looked different with a primer finish as opposed to how they looked when shiny. Some looked better with primer and some not as good.

Richard

Very nice work Rasp, but I´m with Erika too, it all goes so well with the concept at times, to leave rust and blemishes as they come along ... tricky, tricky to know how much to add or not to add ....

[raspero]

This crown is a test casting I made to be sure the gating was right—the real wax is far more detailed and I did not want to risk a bad casting with it—so I am playing around with this one.

I buried it for two days in sawdust soaked with vinegar, ammonia, salt, and urine.



Richard

[raspero]

Okay, I finisher her today:







R

[cheesepaws]

Zoinks! Beautiful!

Very jealous.

Can you tell us more about the braids? Copper?

[Dries]

Very beautiful! Love the green patina.

[mantrid]

It looks fantastic. Must feel great to have it completed at last. The braids are particularily striking and realistic. Its hard to believe they are solid metal.

As you have gone for the traditional verdigris I think I would be tempted to darken the recesses almost to black. To me it gives a less flat appearence.
I think the eye area would especially benefit from blackening as I learnt the Egyptians tended to apply alot of black makeup in this area to protect from sun glare.

[tobias]

I agree with Rika that the surface coloration directly after you nock the mold off is fantastic. I understand that this creates problems cause you can't blend your gates/vents back into the sculpture. Even if you could place your gates differently when you weld the piece together the weld and surrounding area would be discoloured. I do believe that there is a way to recreate this patina using just heat.