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Surubee

Member Since 30 Jan 2012
Offline Last Active Jun 19 2016 09:19 PM
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Posts I've Made

In Topic: Firing A Bowl Upside Down?

30 May 2016 - 10:57 PM

I think I remember hearing an archaeologist once explain that the pointed bottoms of some amphorae and jars were made so they could be easily buried in sand to help keep the contents cooler in desert climates.


In Topic: Raku - Cooling Dunts

07 April 2016 - 10:54 AM

How much difference in thickness is there between the rim and the bottom of the pot? If the rim is fairly thin and the bottom is thick, it could be retaining more heat and the thermal differences could cause the cracking. I cannot tell from the pictures - have you trimmed out part of the foot? If you have not tried it, that might help equalize the temperature variation as well.

 

I also agree with those saying to try a different clay body, or add some sand.

 

Good luck!

 

Susan


In Topic: Wood Duck Mug Wip

09 December 2015 - 11:05 AM

Beautiful work. Glad you are feeling better.


In Topic: Black Clay

19 November 2015 - 11:50 AM

Black clay that you find naturally is often black because of organic matter which will burn out when fired. The color could change to something brown or red after firing. One way you can test it is by making little cones and pinch pots which you fire first to bisque temperature, and then higher if it survives. You can also make a clay ruler to test for shrinkage and another piece to test the amount of water it absorbs after firing so you will know if it is vitrified.

 

To protect your shelves, make sure to fire the test pieces on a piece of scrap shelf or a pad of bisqued clay with raised sides. I have seen tests of these natural clays that have totally melted at high fire temperatures, but are great at lower temperatures. If it has a low melting temperature but a nice color when fired, you may be able to use it as a base for a slip or glaze.


In Topic: Can't Rub Anything But India Ink Into Cone 5 Clear Crackle Glaze

16 November 2015 - 12:28 PM

Someone I worked with used to use a permanent black sharpie magic marker to highlight the crackle glaze on his pots (exterior only). Whatever solvent is in the ink really gets down into the cracks and the marker is not too difficult to wipe off the surface of the pot. I do not think that the color will survive through another firing, though.