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Pouring a wax for bronze.

Pouring a wax for bronze.

Hi all,

Been learning to make my own wax casts for “The Return of Joy” relief. Poor results are below for the first try with pouring wax using the slush wax technique. Often times the first pour yields bad results and knowledge from this makes the next one better.

David from Chico State University worked demonstrated how to do the first wax cast.  He warned me that the wax was going to be troublesome because I made the relief so thin (however, if I had made it just a bit thinner we could have poured the wax solid and therefore the bronze would be solid). The wax would want to clog up in areas and not have a 1/4 inch thickness and remain hollow.  David has been so helpful and generous with teaching me the basics of pouring waxes.

I learned something new, I know it seems like I should have known this but it blew past me somehow.  I just thought that in order to get a bronze hollow with a thin wall you just pour the hot metal in and then out again to have a shell.  Not so!  (I feel so dumbo bumbo).  You have to make the wax hollow and then ceramic slurry is poured around the wax cast but also on the inside of the wax sculpture cast.   Then when the metal is poured into the ceramic shell it travels in that 1/4 inch cavity and makes for a hollow sculpt.  The metal is poured once into the ceramic mold and left there (not poured out!).

David showed me to use a hairblow dryer to heat up the inside of the mold (after it’s all bolted together).  Just blow the warm air for a few moments in the mouth of the mold.  This prepares the silicone rubber to accept the hot wax (220 degrees F) and have it flow better over the rubber.

On the second wax pour, you can use a fan to cool down the wax on the inside of the mold.  Pour the hot wax about 20 degrees cooler (200 degrees F) than the first.  These measures help the wax to not melt away as the hot wax is poured in over it.  Then you slush the wax around and pour out.  Repeat this again until the desired thickness is there of 1/4 inch or so on the wax wall.

Here’s how the first wax turned out. You can see bubbles and dimples and missing areas throughout. Can’t believe I went ahead and fixed up this cast. It took my a day and a half! Way too long.

Dimples and ripples in face very much.

Dimples and ripples in face very much.

Closeup to see much work to be done.

Closeup to see much work to be done.

Bubbles everywhere on slush wax pour cast.

Bubbles everywhere on slush wax pour cast.

After the poor results I decided to try to brush on the wax. Using a deep fryer pan to heat the wax and a candy thermometer to check the temps, it worked well. The chip brushes that I use for brushing on my silicone rubber also work well for brushing on wax.

Brush hot wax onto silicone mold.

Brush hot wax onto silicone mold.

First coat flows on nicely when the wax is very fluid (220 degrees F). Much like with silicone rubber, the initial coat is most important to capture all of the detail.

Next layer is brushed on a bit cooler (200 degrees F) so  the hot wax doesn’t melt the wax underneath it. I did one more layer after that about 180 degrees F. Next I cleaned up the edges of the wax where it meets the silicone so that it will be flush when I join the two halves of the mold together again. First I just used a metal tool to scrape or chip up the wax on the edges that had spilled over. Then I used a soldering iron to melt down the edge. This ensured that I didn’t crack this brittle very hard red wax because I was only melting it down.

Clean up wax on silicone mold edges.

Clean up wax on silicone mold edges.

After joining the mold together and bolting it nice and tight. Then I poured a little bit hotter wax pour at about 200 degrees F. I wanted to make sure that it would be able to get throught the fairly thin mold into all the crevices. I poured it in with a ladel and then slushed it around and poured it out. I did this I think one more time at the same temp. Then another time just around the edge near the opening of the mold where it needed a bit more.

Results were wonderful! Below you can see how well she turned out with little to fix. I did have one area, the fingers that I must have not brushed in well. So that one error took me an hour and a half to fix as I had to resculpt the fingers and nails. I’ll be careful next time.

Pics below show her just as she was taken out of the mold before any retouching.

Fingertips are the only thing that I didn't brush in well.

Fingertips are the only thing that I didn't brush in well.

She turned out great!

She turned out great!

IMG_4202

Closeup to see very minimal repairs needed.

I can see very slight brush lines from brushing in the wax but it’s so very minor; and I’m sure that with a little lamp oil (that’s what I used to smooth out and melt wax when I’m chasing the wax) it  will smooth it out in a flash. Next time I’ll see if I can work it so that no wax brush lines show at all.

Brush lines in wax very slight.

Brush lines in wax very slight.

Well, that’s all for now. Love to learn new things with regard to producing my art into bronze. Every step I learn helps me to know better how to sculpt the initial piece. Now I know that I could have either gone thinner with the relief or wider to allow pouring in the wax with ease.

Thanks for watching and commenting if you like too.

~Tamara

4 Responses to “Pouring a wax for bronze.”

  1. doris says:

    hello Tamara, long time since i visited your blog, and it has happened so many things. this article was very interesting, and i am glad you found with the brush on wax a method that gives great result without need to do repairs many hours.
    do you intend to cast her in bronze, too, or is the wax for learning only ? anyway, you did a great job on her.

  2. Tamara Bonet says:

    Hi Doris :-)

    The first wax that was poured took a day and a half to chase it (the wording used that means to repair the waxes) while the brushed in wax casts took about 6 hours to complete (that includes cutting out the back are for venting and cooling of the metal once poured).

    Right now one of the waxes is at the local foundry at Chico State University. They don’t have what they call ceramic shell casting which captures a lot of detail but another type of slurry that is a mixture of sand and maybe cement (?not sure). First he brushed it into the detail areas of the relief and then poured it over the wax cast.

    Tomorrow he pours it with bronze and then Tuesday he’ll crack it open and see how it turned out. The teacher there is excited to see what kind of quality will come from their technique.

    I’ll keep you posted on to how it turns out! It’s much closer and more affordable to cast there if I can still maintain the quality.

    Thanks for your kind responses on my blog,

    ~Tamara

  3. This is so helpful, Tamara. I’ve been trying to pour my first waxes too. But I’ve been guessing at the wax temp and experiencing some problems too. Thanks for your tips and sharing! Awesome work, as always!

  4. Tamara Bonet says:

    Great Lori! If you pour, really good idea to get a super large ladle so that a large amount of hot wax can be poured in all at once. Try restaurant supply stores where they have all the large cooking items. Thanks for commenting1

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