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High Bridge Pottery

Member Since 19 Feb 2013
Offline Last Active Today, 05:36 AM

#117613 Technical Requirements Skutt Kiln

Posted by High Bridge Pottery on 01 December 2016 - 01:00 PM

The 50amps is just the rating of the kiln sitter, think of it as 'up to 50amps' and if you go over that 50 it will probably break.


I think the general idea for safety is a breaker 25% larger than the kiln but I have run 30amp kilns on a 30amp breaker.

#117418 Am I Screwed?

Posted by High Bridge Pottery on 28 November 2016 - 05:12 PM

They might look better than usual, you never know. At least you found it before it was a 20 hour hold. It could have even worked out at your cone 5 down 6 half way assuming the first time it did hold and you have only added 27min.

#117243 Kiln Conversion Updraft Downdraft Chimney?

Posted by High Bridge Pottery on 26 November 2016 - 05:06 PM

I ended up making a longer video with more footage.


#116836 Is Cone 6 Practical For Domestic Ware In The Uk?

Posted by High Bridge Pottery on 21 November 2016 - 12:36 PM

It is interesting, the clay sold as terracotta has a firing range up to 1220 but all stoneware goes up to 1260/1300.


I think you are probably right that clays sold as stoneware are cone10 clays even if their range goes from 1080-1280. That doesn't mean there is not one out there that would suit cone6 but I have never found much useful data about the clays out there.


I would try a terracotta rated to 1220 and see if you have any luck.


There is one here rated to 1120c but also says 'will vitrify at high stoneware temperatures' after having a look through valentines clay it looks like a few possible cone6 bodys could be filed under white earthenware/terracotta.


"KGM Body     can be fired 1080-1120oC

White to Off White at higher temperatures.

Smooth. Cost effective white earthenware clay which will vitrify at high stoneware temperatures. Due to very fine grog will give a light speckle at the highest te


"Potclays 1141 Studio White Earthenware (LT25)


Smooth. Ivory white very plastic white clay for throwing.1100-1220oC"


Potclays actually give this clay a vitrification range of 1180-1250 but the firing range above. Who decides to put these things.


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#116695 Handles Not Blended

Posted by High Bridge Pottery on 19 November 2016 - 01:09 PM

I am in the no blending club. Saves me 3-5min trying to make it look even and smooth. Never did like the marks sponges leave.

#116618 Stoneware Glaze Unexpectedly Crazing :(

Posted by High Bridge Pottery on 18 November 2016 - 11:09 AM

It does probably have quite high expansion with all the soda feldspar. Lithium will help the crazing. If you have no lithium carbonate you could swap out say 5 of the soda feldspar for a lithium feldspar (if you have that) and see if it fixes the crazing.


Is it leaking out through the bottom? Could be that the clay is underfired even at cone8. Usual rubbish from the company that "Scarva Earthstone Original White matures between 1180°C-1280°C" 

#116534 Clear Glaze Changing The Color Of Glaze/clay Body Below?

Posted by High Bridge Pottery on 17 November 2016 - 07:42 AM

I have seen clear glazes in oxidation tend towards blue in reduction firings on porcelain. Not sure what the cause of it is but reduction brings out the blues.


Here is a quote from digital fire in the blue section, any iron will seem to send the glazes blue in reduction. I think that is giving the blue hue throughout the glaze with cobalt sending the glaze brighter blue.



Oxides - Fe2O3  

In reduction glazes Fe2O3 tends to fire bluish or turquoise to apple green with high soda (boric oxide may enhance). 0.5% iron with K2O may give delicate blue to blue green.


They also say "Iron glazes will move toward blue if alumina is low."


Bit more reading and I found this on another website.

"The cup (fig 4) with iron glazes was fired under reducing conditions. The glaze on the inside contains 0.5% iron(III) oxide and the glaze on the outside 10%; the reducing power of the CO was enough to convert the iron in the inner glaze into Fe(II), but the concentration of iron in the outer glaze was just too high."


#116364 Glaze Ingredients Req'd To Bring Out Effect Of Iron In A Clay Body?

Posted by High Bridge Pottery on 15 November 2016 - 11:30 AM

I agree about the oatmeal spodumene kinda glaze. Seen a very similar effect with a glaze called Oatmeal white. Will see if I can track down the recipe from the friend who used it.

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#115247 Pulling Walls

Posted by High Bridge Pottery on 27 October 2016 - 06:55 PM

Make sure your pot stays /_\ shape for as long as possible. Once you go \_/ it is difficult to gain any height.

#115246 Do You Use Cone Packs In An Electric Kiln?

Posted by High Bridge Pottery on 27 October 2016 - 06:49 PM

Believe in the Prophet Thermocouple and their numbers of destiny!

Beware the False Prophet Thermocouple for he can lead a wayward path and his Replacement may reveal the error of his calibration (or vice-versa).

I have been having bad teachings from my prophet of late. 1080c in the gas kiln with cone 10 down. Always check the reliability of your numbers of destiny with the cones of certain melt 😄

#114825 Epic Fail Making Slabs

Posted by High Bridge Pottery on 18 October 2016 - 01:22 PM

There is a lot to be said for how you recycle the clay. I think most of the shortness is to do with not getting the water in between every clay particle. Excess water over bone dry clay (a good 3 inch of water above the clay line) and multiple mixing over a week or so then another few weeks to let the water evaporate so it was an acceptable consistency to dry out on a plaster batt. It takes time and space, not something everybody can do. I guess I am ageing in excess water instead of mixing and then ageing at the right consistency.


I also try and add all the throwing slop back in to keep as many of the tiny particles or anything else in the water.


I don't like rolling slabs and will get to the right thickness by cheesewiring with a harp or thickness guides and then rolling if I have to. Even if your surface is plaster and not making the clay stick it always sticks to my rolling pin. Finally I can't even roll something the same thickness and get a more even slab with a wire.

#114824 Old Chemicals

Posted by High Bridge Pottery on 18 October 2016 - 12:57 PM


rocks are millions of years old already, a few more won't matter


Does granite decompose and turn into china clay because it is too old to stay as granite, or is it because it was poorly made in the first place?



It is something to do with slightly acidic water disassociating the KNa and some Si from the feldspars and making/leaving kaolin.

#114793 Old Chemicals

Posted by High Bridge Pottery on 17 October 2016 - 07:30 AM


rocks are millions of years old already, a few more won't matter



But how can you be sure?  What if One million and one years is the limit?!!!...Hehe....



You can tell a rock is out of date if it has turned into clay ;) but then it is in date for clay  

#114655 Old Chemicals

Posted by High Bridge Pottery on 13 October 2016 - 11:30 AM

rocks are millions of years old already, a few more won't matter

#114219 Seeking More Technical Understanding Of Firing To A Cone

Posted by High Bridge Pottery on 03 October 2016 - 08:24 AM

Could set up a Wikia http://pottery.wikia...i/Pottery_Wikia