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Delft Clay Goes Crumbly etc


#1

I have been casting with Delft clay and have started running into
problems. The compacted strength of the clay is not what it used to
be and it is getting crumbly and I am having problems seperating
moulds (molds in the US). I have been using talc as a seperator on
all exposed areas.

Now, I suspect it may be:

a) A problem with trapped moisture in the clay as I quench the mould
in a bucket

b) general contamination - while taking care to remove the burnt
clay, there is always something, plus the talc gets in there too.

c) General change over time with repeated casting.

d) It has become too dry as it uses something like an oil as it’s
binding agent.

What I want is to rejuvinate it as on the whole, it seems fine and
it’s quite expensive and I’d like to get as much out of it as I can.
I was wondering if anyone had any ideas?

How about baking it in the oven to dry out the moisture? If it’s
crumbling perhaps adding some olive oil might make it sticky again?

Finally, has anyone tried lost wax casting with Delft clay? i.e.
make a wax model, melt it out in the kitchen oven? then refilling.
That way I could do items with undercuts. I haven’t tried it as I
thought it might be dangerous - especially if the wax was absorbed by
the clay rather than burning out and then exploded when silver was
poured in.

Regards . . .
Cliff Russell.


#2

Hello Cliff, try casting firms who do sandcasting. They often have
oilsand, this is the some stuff as Delft clay. But it is available in
different coarses Delft Clay is just a slim marketing idea. The
proces is already know form the second world war. Just a guy in the
city Delft (Neterlands) has introduced it to the goldsmiths.
Sandcasters know this stuf for years and they purchase larger
volumes, bags of 25 Kg. It stays still expensive but you should be
able to get it for 5-10 dollars a kg.

Greetings
Martin Niemeijer
Ndesign
Netherlands


#3
    I have been casting with Delft clay and have started running
into problems. 

Cliff, I’ve had my clay for more than 8 years, and still in good
consistency. I keep an untouched reserve and add to the ‘user’ clay
when I think it needs it. BUT, I don’t quench. I think thats your
problem. Let it air cool. I also scrape off talc and burned areas with
a painters palette knif…works great without wasting. Don’t know how
to restore other than mixing in some new. Good luck, Thomas Blair


#4

Cliff, Delft Clay is not supposed to be quenched in a bucket of
water. You can tap the mould and it should crumble apart. The clay
that has turned dark should still be ok to cast with. Do not place
the mold with a wax pattern in it into your oven. There is a high
danger of fire. It is very possible that since your clay has been
quenched in water, this has removed much of the essential properties
that keep the clay workable. I have known people who have had and
used their clay kits for some 5-8 years and not had any problems. My
understanding from the vendor is that this product can not be
re-hydrated once dried out.

Thanks for listening,
Phillip Scott
Technical Support & Sales
Rio Grande


#5

If Delf clay is the same thing you can get some here.
http://budgetcastingsupply.com/ It is called petro-bond. Keep i
mind these prices include shipping.


#6

I too don’t quench in water. You don’t really need to. Just pick the
object out of the sand with tongs and quench that. Wait till the sand
cools and scrape the burnt away.

Brian
B r i a n A d a m
N E W Z E A L A N D


#7

I received my Delft casting video about one week ago. It quite
specifically demonstrates the Delft mold/sand being quenched after
each and every pour - in fact, the sand is still flaming while he is
picking the mold up and dunking it in a bowl of water! It was rather
memorable, no gloves needed, just picked it up - flames and all -
with his bare hands and plonked it in the glass bowl…

Regards,
Marianne.


#8

I may be wrong but I was told that Delft clay is whatsand casters
call ‘petrobond’ , see if you can geta sample from a foundry
suppliers.(Someone say if this is incorrect!) Tim.


#9

hello Tim,

Petrobond is the same as Delft clay But ask for the roughness of the
grain. Delft clay consists very fine sand.

A long time ago I have done casting in Cement mixed with oil. It is
very messy but it was cheap ( I did not know of the Delft clay). Just
use cement and motor oil. Mix the oil into the cement, until it is
just bondet. Ratio I do not now just make thick clay. And use a lot of
talcum on your model.

Greetings
Matin Niemeijer


#10
I received my Delft casting video about one week ago.  It quite
specifically demonstrates the Delft mold/sand being quenched after
each and every pour 

Trust us. You don’t need to quench, and it just makes more of a
mess. The casting can be just left there for a couple minutes.
It’ll take you that long to turn off the torch regulators and put away
the crucible, etc. Then seperate the mold halves carefully avoiding
touching the cast metal with your fingers. Push the casting out of
the upper mold half with tweezers or something, seperating the large
bulk of the sand. NOW quench the casting if you desire. But the sand
should stay dry for longest life. discard any sand that’s
discolored, and however much of the talc covered bits as you can
(though that’s not as important).

Peter


#11
    I may be wrong but I was told that Delft clay is whatsand
casters call 'petrobond' , see if you can geta sample from a
foundry suppliers.(Someone say if this is incorrect!) Tim. 

Delft is very very fine. I’ve come across the same colour sand of
another brand in the US and it does not have the detail quality of
Delft. No way as good. It was when I was guest teaching at Revere
Academy in 99 or so. Maybe their sand casting setup is different now.

Brian


#12

I have had success re processing the old burnt clayby adding about
8-10 drops of high flash point oil ie. hydraulic oils and processing
in an old blender. It was not as good as new but suitable for simple
forms. useful when supplies are not on hand or in a class situation
when teaching the basics.I guess this would work for the crumbly
mixture . David


#13

Hey all, Just wanted to let you know that we are in communication
with Delft about why their recommended procedures include quenching
when even our own technical support department recommends that
quenching not be done. I’ll let you know what we find out.

Andrea Hill
Director
The Bell Group


#14
    I received my Delft casting video about one week ago.  It
quite specifically demonstrates the Delft mold/sand being quenched
after each and every pour - in fact, the sand is still flaming
while he is picking the mold up and dunking it in a bowl of water! 
It was rather memorable, no gloves needed, just picked it up -
flames and all - with his bare hands and plonked it in the glass
bowl.... 

Hmmm, I think that I see a sales pitch to get the users to buy
replacement sand/clay…

Ron Charlotte – Gainesville, FL
@Ron_Charlotte1 OR afn03234@afn.org


#15

Is something weird going on here. I bought my sand a few years ago.
I use it about two or three times a month. I just hold the flask
under running water to cool the top, break it open, remove the
blackened part add the same amount from the pack that I’ve just
discarded and carry on. I keep the fresh sand separate from the
working batvch and It’ll be years before I run out.I live in Florida

  • Key West and the weather here is always hot. I don’t seem to have
    a problem with the sand drying out either!

I got the stuff at a show in London and the demonstrator was using a
bowl of water to quench, even then the sand was perfectly reusable.

Tony Konrath
Key West Florida