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Can I fire a cone 5 clay body with cone 6 glazes on it all the way to cone 6?

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Hey all - I recently bought Laguna speckled buff cone 5 clay and have been really enjoying it!  As I'm preparing to glaze, however, I realized my whole stock of glazes are cone 6.   Curious to hear your perspectives on this - have you tried it?  Any tips or tricks to help make sure I don't ruin all the lovely objects I've made?

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It should be okay going to cone 6, most clays have a bit of wiggle room for firing. Exception would be the dark manganese / iron bodies, these tend to bloat if overfired. Try a few pieces and see what happens but I think it'll be fine.

Welcome to the forum!

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On 10/19/2018 at 8:51 AM, Min said:

It should be okay going to cone 6, most clays have a bit of wiggle room for firing. Exception would be the dark manganese / iron bodies, these tend to bloat if overfired. Try a few pieces and see what happens but I think it'll be fine.

Welcome to the forum!

That's great advice, and thank you!  I will definitely post back here with my results in the next few days.  

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On ‎10‎/‎19‎/‎2018 at 8:51 AM, Min said:

It should be okay going to cone 6, most clays have a bit of wiggle room for firing. Exception would be the dark manganese / iron bodies, these tend to bloat if overfired. Try a few pieces and see what happens but I think it'll be fine.

Welcome to the forum!

I have been using Laguna B-Mix 5 of a number of years now and glazing to ^6. The only problem I've had is a very rare bubble in the surface which has been an air bubble in the clay. This has happened on 2 or 3 occasions. The first time around I tried repairing it by grinding the glaze bubble only to find that it went halfway into the clay body (Example below). The repair itself was a failure but the glaze effect of the refiring was outstanding! The pix show the bubble after the second firing; the ground out bubble; the repair; the color change after bisque firing; and last, the failed repair. 

The second firing glaze effect looked really good except for the bubble. The bisque firing caused everything to go yellow, while the final firing (#4) shows the failed repair as well as new blisters along the rim of the bowl. 

While the overall outcome was a repair failure, the information gained in the process was very enlightening!1235810364_01Secondfiringsm.jpg.5f02f66ba7cf71c100b598c667fe61e8.jpg1579799601_02Groundoutbubble.jpg.f5580f02f32871e7c83682075d2ca0c3.jpg859519273_03Thirdfiringsm.jpg.ac540b89a348ac716abeb01f0aaa77f3.jpg734013363_04Failedrepairsm.jpg.4fe889b65b2b705b79a93d36a0d6f902.jpg

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@JohnnyKthose smooth pyroplastic clays like BMix don’t like air bubbles in the clay, sneaky little things. The bloats in the pot after the glaze refire I would put down to the body breaking down and offgassing, bloating again but for a different reason. Heatwork from a second glaze firing to the same cone can do this, if you have a cooler area in the kiln I would suggest putting re-fires in that area or firing a cone lower than the first glaze firing. Re-fires are always a crap shoot but going to a lower cone lessens the chance of these type of bloats. 

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JohnnyK

crystalline glaze is often refired to 1350F: called a "strike" fire in our little world. The metals in the glaze ( copper, iron, and cobalt) are re-oxidized which changes the color.  There are a few who strike fire uo to bisq temps, but 1350F is all that is required. Any glaze that has these metals will react, makes for interesting variations.

T

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I have fired quite a few pieces with that same speckled buff to ^6, with beautiful results.  In fact, I actually like that it comes out a little lighter buff color.  

 

bellymugrim.jpg

 

I suppose I should mention; I'm firing oxidation.  Can't speak to results with reduction.  

Edited by Apocalypticamerica

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If you're taking clay/glaze to a hotter temperature, it's a good idea to put it on a waster piece of clay.  Then if it does over-melt and form a puddle, it won't ruin a shelf.

Edited by Chilly
Typo

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Same as Denice.  I usually mix the Speckled buff with other cone5/6 clays.  Will get occasional warping with things like yarn bowls so I add a little extra sand and fireclay.  For usually items like bowls and mugs that WC-403 clay does fine at cone 6 (and even cone 7 when first firing my new kiln). 

I also bisque to cone 04 and this helps burn off some stuff that can cause glaze issues. 

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On 10/21/2018 at 9:27 PM, Apocalypticamerica said:

I have fired quite a few pieces with that same speckled buff to ^6, with beautiful results.  In fact, I actually like that it comes out a little lighter buff color.  

 

bellymugrim.jpg

 

I suppose I should mention; I'm firing oxidation.  Can't speak to results with reduction.  

That's so wonderful to hear :) Thank you!

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