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earthfan

Member Since 11 Mar 2013
Offline Last Active Feb 10 2016 07:51 PM
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Posts I've Made

In Topic: Spodumene

28 January 2016 - 09:12 AM

The spodumene supplied by the Greenbushes mine is a fine sand that is 88% spodumene and 12%silica.  I fired a little bowl of it to about cone 7 and it converted to beta spodumene, puffed up and turned into a fine pink powder. It did not melt at that heat and didn't even fuse to the bowl it was in. Spodumene has one molecule of lithium oxide to one molecule of alumina to 4 of silica, so it is like feldspar, but with a lower proportion of silica. Spodumene has a negative co-efficient of linear expansion. It doesn't shrink when fired, it gets bigger.

 

Lithium carbonate is Li2CO3 and is slightly soluble. That is what you need to spray on the raw clay to get a sheen.

 

"Ceramics Monthly" of February 2015 has an article on spodumene.


In Topic: Look At The Gallery Today. Imprints Of Plants Is Marvelous

21 November 2015 - 08:19 AM

Where is the website?


In Topic: Setting Up And Basic Tools For The Total Beginner

13 November 2015 - 12:25 PM

Don't neglect the traditional hand-building methods. It takes a lot of practise to make a large pot on the wheel, but by using coils, a complete beginner can make a large pot at her first attempt. Slab building also has much potential because you can add texture in ways that are impossible on a wheel. A good tool is a long pastry rolling pin and sets of two wooden slats the desired thickness of the slab you want to make. Even better is a potters' harp, but I don't know where you get them nowadays.

Always make everything bigger than you want them to be because of the 12% to 14% shrinkage. The limitation with wheel thrown pots is that they always come out round. They can be coaxed into ovals and squares, but there is never the shape variation that is available when using coils.

I don't know what sort of wheel you have. Mine is a Venco and it can be easily converted to a work table just by placing a piece of chipboard over the top. Discarded cupboard doors are a good size. Again, fibro cement is the ideal work surface for slab and coil work, so long as it is dampened. Place it over a sheet of plastic to protect whatever you sit it on.


In Topic: Duncan Gold Luster Question

12 November 2015 - 11:27 AM

A different issue: I want to apply lustre to stoneware. Would it fire onto a glaze that was already high fired, or would it require a layer of glaze that would fuse at a lower temperature?


In Topic: Setting Up And Basic Tools For The Total Beginner

10 November 2015 - 10:21 AM

If you are in Australia, you will have access to fibre cement, which is the best stuff for wedging tables and bats. Fibre cement has a smooth side and a textured side, and, when dry, it sucks water out of slip very quickly. When using it as a work surface it will be necessary to keep it damp, or it will dry out your clay too soon. (Make sure that it isn't asbestos cement.) It is fairly cheap at Bunnings and local hardware shops. You can cut straight lines with the scoring tool they sell for the purpose, but you will want round bats when you start to throw wider things. An angle grinder with a masonry disc will allow you to cut out discs of fibre cement. If possible, get your wheelhead fitted with two removeable pins.