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[again] Delft Clay mold


#1

Hello Lars,

Some time back you wrote about a Delft Clay mold for casting. I
have never heard of this product - can you tell more about it?
Where does one find it, etc.? I tried cuttle bone casting years
ago - it was successful, I should try it again.

TIA
Lorri Ferguson
fredlori@worldnet.att.net


#2

The Delft sand casting set is excellent. Rio carries it and it
comes with a great video. This method has a lot more potential
than most people realize, especially for simpler designs,
including rings. You can create an accurate mold and cast a piece
in about 15 minutes, 20 if you are really working slowly. The
results can replicate very fine detail, such as the relief on a
coin, with great accuracy. Plus there is little chance of
porosity or other complications. We usually teach this method as
a small part of our casting classes and people are always
surprised that sand casting can produce high quality results so
easily.

In my estimation, this method is vastly under utilized, probably
because it is so low tech.

Alan Revere
Revere Academy of Jewelry Arts, San Francisco


#3

You can get it from SWEST. The product is called “clay”, but in
truth, it’s just a very, very, fine grained casting sand (A
commercial product). Petrobond, I think (not sure). Organic
binder, probably oil. The key to it is that with that fine
grain, it gives you very good surfaces, almost as good as lost
wax casting. No “sand” texture at all. Well hardly any. And
the oil binder means the mold is a “reducing” atmosphere, so
castings come out remarkably clean and bright. The product is
sold with a little set of “rings” for a flask/mold frame, which
work, though they’re really pricey. It takes a bit of practice
to learn to make the molds for these things really work well, but
it’s all in all a quite useful tool. I was reluctant for quite a
while to pay their price for it, but now, having done so, I have
to say it was probably worth the money. At least to me, in terms
of time saved and/or jobs done with it.

Peter Rowe


#4

I have seen this product, or one very similar to it,
demonstrated at a trade show. It consists of two deep rings which
fit together to form a deep (about 4cm) cylinder like a napkin
ring. The diameter is about 5 or 6cm. Esentially you pack the
bottom cylinder with the clay, tamp it down and then insert your
item to be moulded, tamp that in place, dust it with talc and
then fit the upper cylinder. Then you add more clay and tamp it
down. Finally you separate the two cylinders, remove the model
and then cut sprues and passages for the air to escape from and
reassemble the tow rings. There is a line incised on the side
which allows them to be registered exactly. Final stage is to
pour in the molten metal. It seems to work very well, at least
the guy doing the demo made it look easy! My father has tried it
and said that it works very well with a bit of practice. Cost was
about 40 UK pounds including a crucible and about 1kg of the
clay, which is reuseable. I’ll try and get some details of the
supplier as I have it in a catalogue somewhere at home.

Alex
Alex Ball
Electron Microscope Unit
The Natural History Museum
London SW7 9BD

Tel 0171 938 8973/9348
Fax 0171 938 9268


#5

Not sure if this has been identified yet, but Rio Grande sells
it in their Tools and Equipment catalogue. Email me offline for
more info, or just get them to send you their catalogue. It’s
around $80 U.S. if I remember correctly! -Kieran


#6

Hi Lorri, I bought my Delft Clay system at a local supplier here
in Sweden but I’ve seen it in The Rio Grande catalogue as well.

The whole system consists of two aluminium rings (approx. 6 cm in
diameter 2.5") each 2,5 - 3 cm high (1"). The clay is a red dry
very fine grain sort of casting sand. The procedure is similar to
sand casting but it is really easier to get a good quality
casting out of it.

It’s easy - you turn the bottom ring up side down - stuff clay
into it and pack it by pounding with a hammer (not too hard
though) - remove excessive clay from the bottom bu pulling a
metal ruler over the ring. Turn the ring right side up and the
you press your master object (no undercuts) half-way into the
sand - you can then add chunks of sand if necessary to make sure
that there is no under-cuts for the other half.

Now you powder with talk and apply an even talk layer with a soft
brush. Add the upper ring (there are index marks to align the two
parts) and stuff the upper ring with clay and pound with hammer
and remove excess with the ruler.

Next step is to separate the two rings from each other and remove
your object. Then cut the sprue (pouring hole) - if I fail
somewhere in the process - this is the time. You have to be very
careful when you cut the pouring hole as it is very easy to
damage the form you’ve impressed.

Don’t forget to make vent holes as well - the position of these
are are or less obvious when you see it.

Now just put the two rings together using the index marks for
alignment - melt the metal in a cubicle and pour when you’ve
reached the proper temperature (silver looks like mercury and
with a mirror surface) - Do not pour to early - the mould is not
hot and the metal will get stiff before filling completely.
Chill the whole thing in cold water and separate the rings from
each other and remove your cast cut the sprue and vents and
finish.

The clay is reusable - you just have to remove the burnt parts
(the clay that had contact with the hot metal). One bag of clay
(approx. 1 kg) will be enough for about 90 castings.

The neat thing is that if you make a mistake - you just do it
again - nothing lost in the process…

It is really simple but I recommend that you get the video tape
(usually included in the complete set) and then you just imitate.

I’ve made approx. 30 castings and failed approx. 5 - because I
forgot to vent properly or poured before the metal was at the
right temperature.

One complete cast is perhaps 5 - 10 minutes (non experienced) so
it’s quick to test…

Good luck…

Best regards
Lars Dahlberg/Gotland/Sweden


#7

I have a question about the Delft method. I recently added a
line of sand cast pendants which are supposed to be similar to
artifacts found in Northeren Europe, so I wanted them rather
rough looking. I am using the Delft rings and sand. I
definitely get the rough look. It is fine for what I am doing
but if I wanted something nice and smooth I am not achieving it.
Am I doing something wrong? I use silver scrap and reuse the
buttons. Would I have better results if I used a better ratio
of new silver to used?
Thanks for any answers. You can see what I am doing at
http://www.designjewel.com/cast.htm Any comments would be
apprecieated. I’m sure I will want to use the method for more
sophisticated looking jewelry in the future. Jan McClellan