Making Clay slumping moulds

[Ian]

HI
At last I got photo's taken resized etc so now we can get to it. The first one I will describe was a mold for a kilnformed lampshade that was dome shaped and had 6 slumped panels made from blue and white streaky opal glass. I had just got back to East London from Johannesburg with my first kiln. Talk about being thrown in the deep end. I did'nt even know my kilnwash from Bullseye Glass!
Anyway there were 3 of the panels in this glass shade that were broken so Beth de soldered the broken panels and I managed to stick the pieces of one of them together to use as my positive shape to make a mould from. What I had to to was first use the panel to make a solid shape so that I could take an impression of it. This was then stuck down to the bottom of a wooden box with removeable sides so that the box could then be filled with plaster of paris.



Imagine the shape of the panel mould in side this box. once the plaster was poured then it was left to set and then the panel mold was removed from the plaster of paris leaving this negative mold




Now comes the fun part. I then poured Raku clay slip {just a runny mixture of clay} into the plaster and what happens then is that the dry plaster of the mould sucks the water out of the clay slip and you can watch as the color of the clay changes as it solidifies from the walls of the plaster mold inwards towards the centre of the clay slip which fills the entire mold. You wait until the the color change reaches approx 3 eights of an inch thick and then you pour the still liquid clay out of the mould leaving behind a skin that covers the whole of the inside of the plaster mold.When this has dried to what they call the leather stage it is still slightly pliable and you con remove it from the mold and cover with a damp cloth so that it dries without warping or cracking. You now have the clay mold that you fire or have fired to the bisque stage at a local pottery place. This then becomes your slumping mold Just kiln wash and use as normal.







I used Raku clay because it can take temp changes better then other clays Make sure that your Plaster of Paris mold is bone dry before pouring the clay slip into it.
I made three of these molds and found glass to match and the Beth worked out a pattern for the panel and I then slumped all 3 panels in one firing
I opened  the kiln the next morning and I had three perfect panels devitted to hell and back!! This is when I found that you do not take a kiln manufacturer's word on any thing when it comes to actually using your brand new kiln and actually firing glass
But thats a story for another day
The customer was very happy to get his old lampshade back with new panels in it
One thng to remember is that clay shrinks when drying and again when being fired  Like this The fired clay mold inside the plaster of paris mold





The next project was to make a plough shaped mold because at that stage you could'nt get them in South Africa. So first I made one in wood that I turned on my lathe



I then made the Plaster of paris mold pouring the plaster into the box former with my wooden shape inside and then removing the wooden shape from the plaster mold and ended up with this



Then poured the clay slip and ended up with my slumping mold drying in the plaster mold
Took that out of the plaster mold and had this




And then fired it to bisque and now before I use it I have to drill the 4 holes on the bottom to allow air to escape when slumping. I also wanted to try this shape with a foot ring Heres a side view and a view of the bottom of the mold to show the marks made when pouring out the slip  






I think thats about it Any questions will be answered with pleasure
Ian

[nansea121]

Very informative. Thanks Ian.

Try copying the photo links from 'IMG images for message boards' when in PhotoBucket. When you have transported those links you can click on Preview and you should see the photos in the body of your message.

[Ian]

Thanks Guys
I found the problem
Ian

[Kev]

Very cool Ian..thanks!

[Judy K]

Great info. Thanks

[ct4mom]

This is great, thanks for doing this Ian

[Anne]

Thanks Ian.  I want a drop mold that's got a smaller interior hole than what I can buy.  This will help me make that mold if I can't find something usable in a ceramic store.

[Becki]

Well done, Ian. At what temperature did you fire these to bisque?  Or does it depend on the clay?

[Ian]

 Thanks guys Glad to be of help Here are a few other molds that I made



This is a two part mold closed and the clay slip is poured into the holes One for the small leaf and one for the med size leaf This a mold that I bought

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Here it is opened to show the 2 different leaves





And here are the clay molds ready to fire in my pottery kiln.





 The 2 smaller ones are made in the mold in the pictures. And the big one is a bisque fired bought from a potter here in town. I can't find a mold for the big one.
The beauty of being able to make your own is that my kiln can take about 20 of the small leaf mold on one shelf and I have 3 shelves next to each other. So I can slump 60 in one firing. 60 of these molds would cost me here in SA about 50.00 rand each. Making them will cost approx R3.50 each.
And having all your molds the same and being able to fill the kiln you only have to work out one firing schedule because all the molds are exactly the same size, depth and span.
The same goes for the other 2 sizes. I only need to work out  a schedule for each size

Anne A suggestion for your small dropout ring. If you make one out of a square of ceramic fibre board with a hole cut out of it with a hole saw and then hardened you can try it out for size in one firing to check if your finished dropout is exactly the way you want it and if it is the use the fibre one as a positive to make a clay one for permanent use Making a fibre one first is quick and easy. The reason for making it square is the you then have more space on the outside edges for place to have your kiln props
Becki I will go out tomorrow to the work shop and check the firing schedule  for firing to bisque
Once again thenks for the kind comments all of you. It makes it worthwhile
Regards
Ian
This is the toploading pottery kiln and it will take 4 shelves ontop of each other and this the setup I used to make a dropout for a local hotel. It had to be 14 inches long and about 8 inches in diameter using 4 sheets of 4 mm glass

[Kev]

Man..that talent and skill! Awesome!

[Anne]

Ian, how long did the drop take once it reached max temp on the one you made for the hotel - the 14" one? I did a small one yesterday that took almost 2 hours, just wondered if it's faster using side elements (not that I'm going out and buying a new kiln, just curious!)

[Malinda]

Wow, Ian...love the tutorial / info. Thank you for sharing!

[Ian]

 Becki The slip I use is Raku clay and the bisque firing temp is 1650F
Anne I fired the long dropout at a low and slow schedule the drop time was 4 hrs 43 min. Total schedule time was 27 hrs because I was being very conservative and the glass was 16mm thick at the top so I I had to anneal for that thickness
Here are the pic for a fibreboard dropout mold that I made this afternoon to see how long it took Just on 7 min. Now I will soak it in rigidizer and fire in the kiln to harden This one has a 4 inch hole so I used a jigsaw to cut it out and then rounded off the inside edges with sandpaper. Just like working with Balsa wood.
I use a lot of different size cut up fire brick for props I find them a lot more stable and they give a lot more support to the mold And yes I do kilnwash them
Regards
Ian

[Becki]

Thanks, Ian.  I don't know if I'll ever be that ambitious but if I do it's nice to have the info!

[Anne]

Like Becki said!!  Thanks Ian! But I am going to check around the area to see if I can find some fibre board!. You just never know when someone is going to post something cool and it just tweaks an idea that was rolling around in the subconscious!

[Wayne]

Like Becki said!!  Thanks Ian! But I am going to check around the area to see if I can find some fibre board!. You just never know when someone is going to post something cool and it just tweaks an idea that was rolling around in the subconscious!

Last November I attended a workshop which featured the pre-fired Kaiser-Lee fiber board.  Among all the things that can be done with it, I asked a lot about the creation of a drop from the board and found it to be a snap. 

The other potential parts is that you can sand a pattern into the board an reproduce that in the glass as it is being dropped.  Carving the board is done by using a fine sanding sponge and is super easy to do.

I also bought Petra's book while at the distributor's workshop.


http://www.kaiserlee.com/

[Anne]

thanks Wayne, I found a supplier for them that's only a bit over an hour away from us! I like the idea that you can sand a pattern into the board too.

[Becki]

Check the prices on both, Anne.  Fiber board is usually less expensive than KL board and can do the same thing.

[Anne]

thanks Becki, the KL IS really expensive! Ian, can I sand the fibre board? Would like to have a ruffled top on it.

[Ian]

Anne  Yes you can. You can also use files or any fine abrasive instrument. A Dremel with all the different cutting burrs. Experiment with them all . Just make sure to wear a face mask.
Ian