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john rigoni

Fabricated Pitch Bowl And Homemade Pitch

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My inspiration came from a post earlier, on this forum: http://www.thecarvingpath.net/forum/index.php?/topic/1543-metal-half-ball/page__p__13628__hl__+pitch%20+bowl__fromsearch__1#entry13628

 

First, the pitch bowl. From what I've read, the common practice is to fill your pitch bowl with lead up to one inch from the surface. This adds weight and reduces the amount of pitch you need. Not too keen on melting lead in my small space, I opted for a fabricated bowl from 1" plate that I had in the shop. At the steelyard I found a section of pipe 10"x 1/2" thick. I had them cut a 1 1/2" section of that for the top.

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Seven long days of weld, chip and weld again produced this massive half a cannon ball. I had a good number of welding rods I didn't like, so this was the perfect project for it. The bowl weighs in at 56lbs. I'm letting it rust fully, might help to prevent it from slipping? It's an experiment. It's starting to look like a planet after the etch..

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Now for the pitch. I've watched Ford Hallam's videos enough that I had to try and make his pitch.

He mentions the formula on the carving path: http://www.thecarvin...opic/905-pitch/

All the ingredients are easy to come by except for the pine rosin. You can buy this on brewer websites for $20 a pound. I live in Houston, Tx and am surrounded by pine forests, so I will try my hand at gathering what is out there.

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Turns out burning the pitch ruins the properties, so here is my second attempt. I found another national forest nearby and after several hours, scrounged 1kg of sap. woohoo! I cooked this on a hotplate and it never caught fire. The unburned batch remained a dark brown. The first batch that was ruined, turned black. Now for the conversion from pine rosin to useable pitch!

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so it is just used to hold metal in place while it is worked? to release it do you just heat the pitch again?

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seems like this is used in all the examples for working metal can it be used for stone or wood carving or would the pitch cause too many problems?

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I believe that the pitch needs to be torch heated to remove the item that it is holding. Wood is flammable, and I would guess that stone needs a very slow and even heating. Maybe using a hair dryer might offer a safer yet slower heating, but wood is likely to dry out more than one would want it to when hot, dry air is aimed at and around it until the pitch could release it. Would the pitch also stick terribly to the materials?

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i was thinking you heat the bottom of the bowl to release the iteams that way you keep the metal from being burnt as its being released.

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Ok, I mixed the rosin with Mr. Hallam's list of ingredients; vegetable oil, plaster of paris and a bit of charcoal powder. I poured it into my bowl and after it cooled, found that it didn't stick at all. I'm guessing the density of the bowl made it a massive heat sink. The pitch popped out into a perfect wafer. Other smiths suggested I heat the pitch bowl first. The thing weighs 56lbs and was denting in my oven, soo. . .I set a fire on top for awhile and then poured the pitch in. So far everything looks good.

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