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Problem with cleaning bronze after casting


#1

Hello

start to cast bronze.

bronze=cu88 sn 12

casting is OK but after kenching the tree in Hydrochloridric acid to
remove investment a white film covers the casting pieces, difficult
to remove. I the temp of the flask 700degres, pieces are thin. near
filigree work) the pieces are quite thin and using sand blasting or
high pressure water jet will deform the pieces thsk by advance for
your help.

nathalie


#2

There is so much to say and I do not have the time right now.

Do not use Hydrochloric acid for investment removal. It is too
strand an acid. We do not use any a cit for investment removal, we
use ultra sound unit and if that is not available an old toothbrush
and running water. It helps to put the can/setup into water while
still somewhat hot, BUT not too hot (wait for to or 15 minuted after
casting then put the whole can in water. The temperature difference
of the hot can/investment/metal and the cold water causes lot of
breakdown of the investment, the more temperature difference of the
can and the water, the more breakdown of the investment.

What metal are you pouring? 700 deg. is that F or C? If F I think it
is too cold, we pour mostly by “color” inside the cavity to be
filled, we shoot for a deep red and it is far hotter than 700 F. If
you are measuring C then you are close to the correct temp but if
you have fine areas to fill, the filigree, metal and flask
temperatures may both need to be on the hot side. Are you gravity,
vacuum, pressure or sling casting. Straight gravity is often not
enough to get filigree to fill, you need to “assist” the metal into
the smaller areas, thus vacuum, pressure or sling is needed.

Art the thin pieces supposed to be thin? If they are supposed to be
thin, use other cleaning methods that blasting or high pressure
water, , an old tooth brush, a very short cut bristle brush, etc.
to clean the investment. Final cleaning in an ultra sonic, if
available.

This is not very inclusive of ideas/thoughts, but it may be of help.

John
john dach


#3
casting is OK but after kenching the tree in Hydrochloridric acid
to remove investment a white film covers the casting pieces,
difficult to remove. I the temp of the flask 700degres, pieces are
thin. near filigree work) the pieces are quite thin and using sand
blasting or high pressure water jet will deform the pieces thsk by
advance for your help. 

Don’t quench in acid. quench in water. Quenching in acid won’t
improve the situation, and can be quite dangerous. After quenching in
water, then you can use an investment remover if you wish, some of
which are based on acids, but not all. The commercial products work
better than HCl. Some, based on fluorides, also need to be used with
care, but can work quite well. I’d suggest contacting the
manufacturer of the investment you use, or alternatively, your metal
supplier. They often can offer specific suggestions that work best
with the products you’re using.

Alternatively, an ultrasonic generally will do the job nicely. It
may be easier to cut the castings off the tree and finish cleaning
off that film afterwards.

Steam cleaning is also useful, and is much gentler than a high
pressure water jet.

Peter


#4

Hello John

Thanks for you reply
i’m pouring bronze= cu 88 and sn=12
the temp of the flask (can) is 700 celcius, as it is very thin work

thks best
nathalie