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A Bramblebush Workroom Project
Repousse`/Chasing
A compendium of miscellaneous information
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Page 04
Jan. 8, 1999 - I have been reading the discussion on chasing and repousse and chasing and the topic of using pitch. I hope the following information adds to the discussion and helps my fellow smiths.
You can buy the prepared black pitch from a number of suppliers, however this black pitch is usually very hard and brittle for my likes. To mix a quantity of pitch that would fill up an 8 inch cast iron bowl (approximately 5 pounds or more) I generally change the recipe by slowly melting in blue injection wax (used in casting). I put in a small amount at a time until the pitch is smoother and softer when warmed with heat. Then I melt and mix in about one tablespoon of lard. The lard makes the pitch sticky but a bit more resilient. To tone down the now sticky texture, I gradually sprinkle in casting investment while I am warming and mixing the pitch.
Test out the pitch and it should grab metal well but when warmed should release the piece cleanly. As clean as pitch can be!
I should add that extreme care should be taken when doing all this mixing, because the pitch is hot and you can burn yourself. Do not let the pitch sizzle like bacon when heating (it makes it brittle) - that means that you have it too hot and it is dangerous as well. Mix slowly and carefully and if you do get any on your skin, put your hand immediately under cold water. Do not pull or pick the pitch off - after you have cooled the burn under water for some time, then dissolve off the pitch with mineral spirits.
When you put the piece into the pitch bend up one corner slightly so that you can use the corner later to pull your piece out. To get the pitch off your piece after you have finished working, heat the piece with a low soft flame and as you are warming the piece with the torch grab the corner with pointed tongs and gently pull. Solvents are recommended for dissolving the pitch off the piece or you can burn it off by reaching annealing temperatures.
All methods can be dangerous so use extreme caution. I remove most of my pitch from pieces by annealing until the residual pitch just begins to turn to ash. This technique does require a powerful exhaust hood over my working table because the remaining pitch does catch fire for a short time as it burns off.
There are other commercial pitches out there and I use three basic kinds that vary in hardness. By the way, pitch can get expensive in large quantities - if I am working large scale then I change my strategy and materials.
Dianne deBeixedon
Jan. 8, 1999 - Â Burning off the pitch works only with copper, brass e.t.c. For sterling you can use the lacquer thinner or any solvent which can clean the type of pitch you have.
For example, a regular black pitch can be removed from the metal with Naphtha. Having an appropriate ventilation is absolutely important in both cases.
Valentin Yotkov
Jan. 9, 1999 - I've just reread this thread and I don't think that anyone has talked about the advantages of starting a piece by hammering the first depression with a rounded mallet or using a die to get a lot of depth quickly.
I was in a workshop with Marcia Lewis last summer. She had us start one piece using a wooden die with wing nuts. This type of die is described in many books for making duplicate shapes. It requires a heavier metal if you want a lot of depth/height.
The metal could also be started in shapes carved into a wood block or raised or sunk by traditional means depending on the size of the work. It is then worked from the front to refine it and of course it can be flip-flopped to its backside again.
Marilyn Smith
Jan. 9, 1999 - That is true Marilyn and Lee hasn't piped up to suggest the obvious advantages of doing the basic image of an edition with a die and a hydraulic press.
Obviously we put a lot of value on hand finishing, but the initial draw downs can be speeded up. Like a master having his apprentices take the stone down to the last few inches. Except we have mechanical minions at our disposal.
I do have a question on this end, How much power is needed to form an image.
Say I have a large pendant 3" x 3" how big a press would it take to draw something to 3/4" relief. How much pressure?
Say again, I am doing a freize in panel sections, 12" x 16" again 3/4 relief. Â How big a press for this?
Gene Olsen
Jan. 9, 1999 - On one of my parts ,I press form it to a depth of 1" in an area about 6"x6" into .040" steel with my H frame press, which is powered by a simple 30 ton bottle jack. To get to that depth I am not stessing the jack or press at all. I would think to form thinner annealed copper sheet in a press, would be quite a easy task.
The bottom die could be made of wood, or even bondo placed on top of a 1" thick steel plate, for the top die all you would need is a 1" thick soft rubber pad backed up by a substantial flat steel plate (3/4- 1" thick.
After forming just as you said detailing and deepening would really distinguish the piece.
Wray Schelin
Jan. 9, 1999 - My home made press uses a 12 ton jack and could press an inch in the copper. My press is not bolted down which would make it easier. I would love to have one of Lee's with the nice gages and the springs but. . . .money money money. A sand bag or a shape carved into wood used with hammers or rounded dowels will also work
Marilyn Smith
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