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Pitch Problem


#1

Hello All-

I am having an odd problem with black pitch. Normally, the pitch is
relatively hard once melted into a vessel, and has minimal
compression when hammered. However, a student put pitch in her
vessel, and as she hammered it started gradually squeezing out. It is
soft and a bit tacky–I could easily stick my fingernail into it and
rip off a piece. I thought that there could have been a contaminant
in the vessel, so we melted the pitch out, cleaned the piece up, and
put brand new pitch in. The same problem is occurring.

I have no idea what to think. I have used pitch numerous times in
the past, both in my own work and with students, and I have never
seen this. The pitch seems normal before we start–we have to break
it into pieces with a hammer. Any thoughts on what is happening?

Thanks in advance.
Erica


#2

Pitch can be from very hard to very soft and this can be controlled.
The hardness used will depend on the type of work you are doing. I
have used several different pitch types over the years and found
Allcraft in New York to have the best and most consistent. The two
primary I am familiar with are black and red. Allcraft can advise
you on which is best for your needs.

The hardness can be adjusted by adding oil (I use olive oil for the
high flash point) to soften or powder to firm. Many different
powders work and I use talc. You will need to experiment with the
powders, as too much can have an adverse effect on the pitch. When
doing fine detail you could try a trick I’ve used. I like to have a
very soft pitch, but the piece moves too much in the bowl. After
placing the piece in the pitch, freeze the whole bowl. The pitch
under the work area will soften immediately for the fine work, but
the rest will remain hard for a while to support the work. Refreeze
as necessary.

Hope this helps,
dan


#3

Erica,

However, a student put pitch in her vessel, and as she hammered it
started gradually squeezing out. It is soft and a bit tacky--I
could easily stick my fingernail into it " 

Is this a problem? I don’t use the black pitch, but the red german
pitch and after chasing a while on the vessel, yes it does seem to
squeeze out. But mine isn’t sticky unless the room is warm. I do
believe that the hammering against the vessel causes the pitch to
shift and try to get out of that place you have it in.

Jennifer Friedman
Ventura, CA


#4

I’ve had good results using plaster or brick dust to stiffen my
black pitch, powdered clay works too. Seattle pitchworks stuff is
great and not petrolium based, but since you already have the black
stuff use it.

There is some good in Oppi’s book concerning recipes for
mixing.

In chasing on a bowl I’ve found it benefical to sink a large bolt or
railraod spike in the pitch so when it’s set up you have a handle to
clamp it in a vice or screw it into a hole for stability. I have my
bowl set in a lawnmower tire with the center removed.

J.M Richardson


#5

Was talking to a jeweller friend yesterday who used to use plaster
of paris to harden the pitch - I personally know nothing about
pitch/pitchbowls or anything of that nature, but thought the info may
help someone somewhere!

:slight_smile: Kimmyg
www.northcoastbeadmakers.com


#6

Thank you all for your responses and ideas–I’ll give stiffening the
pitch with talc, plaster powder, etc. a try. Thanks, Jim, for the
Untracht suggestion–the section on pitch is right here in front of
me.

The pitch in my student’s vessel hardened up again on its own–it
seems that the temperature of the room caused the softening of the
pitch. The studio was extra warm when I first posted and is
significantly colder today.

Best,
Erica