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kenthenricksen

Pitting and pinholing

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Hi Rick Wise!

Are the pinholes on the sides facing your kiln elements appearing throughout the load, or just on top/hottest shelf? Only nearest the elements or any/all surfaces that get direct radiant from th' elements? Got any pics to post? Any other helpful info, e.g. what clay body, did the firing hit your heat work target and how do you know, what glaze/formula...

I had some tiny bubbles in clear (Kitten's Clear ) when I've run a cone too hot by mistake - but the lil' bubbles are all over.

Bill and Magnolia might have missed that your post is tagged onto an older thread...

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Bill may have confused my question with an earlier one.  I repeat:

On 2/15/2019 at 2:47 PM, Rick Wise said:

I get some pin-holing but only on the side nearest the electric elements in my kiln.  I'm sure that is telling me something but I dont know what.  Too hot?   Suggestions for avoiding this?

To clarify, this happens in the final glaze firing.  The glaze is my glaze -- not a commercial glaze.  There is no sign of bubbles or other problems when applying the glaze -- the pinholes appear only after firing in the finished pot.  And, as I said, only on the side nearest  the elements.

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1 hour ago, Rick Wise said:

Bill may have confused my question with an earlier one.  I repeat:

To clarify, this happens in the final glaze firing.  The glaze is my glaze -- not a commercial glaze.  There is no sign of bubbles or other problems when applying the glaze -- the pinholes appear only after firing in the finished pot.  And, as I said, only on the side nearest  the elements.

I know the original op had bubbles, did you feel packed bed porosity was not worth testing or have you tested and feel confident it is not an issue?

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Describe the 'pin holes' more thoroughly.  Is there an unglazed clay surface at the bottom of the pin holes?  or are the pin holes blisters that have burst and leave a glaze coating over the bottom of the hole?

My hypothesized explanations: 
A.  The first could be a consequence of the side next to the coils heating the applied glaze fast enough that the gas in the surface pores is punching a hole through the powdered glaze ingredients.  While on the cooler side away from the elements the gases are escaping more gently between the powdered glaze particles and not creating holes. 

B.  If the holes are healed blisters, the glaze is likely forming a melt before all the gas has been expelled from the pores in the bisque ware and the glaze melt is not 'strong' enough to keep the gases from bursting through the melt.  Either 

Some questions about the glaze:  is this a very viscous, stiff glaze?  Does the glaze have a high surface tension?  put another way, does the glaze run much? and when applied thick does the glaze spread out or roll up at the edge between the glazed and unglazed areas? 

Photos of the pinholes and the non-pinhole areas would be helpful in troubleshooting via the forum.

LT

 

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