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ErikEitel

Amaco Rutile Glaze Separating

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Hello:

 

During my recent glaze firing I had an experience that I've never seen before in that my glaze looks like it's separated from my work. However, it seems to be a little more complicated in that the glaze is all over my shelves (Ugh. I know). I've attached a picture of a piece from this firing so you can see what I mean. Some piece are worse than others.

 

The glaze that was used is this: https://www.amaco.com/products/glaze-pc-20-blue-rutile

 

The Clay in use is this: http://www.lagunaclay.com/clays/western/wc379.php

 

The ware was fully bisque fired prior to the glaze firing, and the glaze firing went to cone 6.

 

Any advice would be appreciated.

 

Thanks!!

post-80335-0-50822200-1478279374_thumb.jpg

post-80335-0-50822200-1478279374_thumb.jpg

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You may try posting your question into Facebook's "AMACO Cone 5/6 Exchange" group. It is a discussion group for Amaco midrange glazes users also being monitored by Amaco employees. If somebody knows something, they should be able to help.

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Have you had success with this glaze and clay before? Or is this a first time use/problem for the glaze?

 

Did you lose glaze only on exteriors or also the interiors?

 

What was your firing cycle? Slow, fast? Long soak at peak before cooling? Did the kiln over-fire? PC glazes are rated cone 5/6, to which cone did you fire?

 

Is there a possibility your hands were dirty/oily during handling of bisque that would prevent the glaze from adhering to the ware?

 

Some glazes using Gerstley Borate can eject glaze off the ware during firing; some times that can happen with high cobalt levels. The PC glaze is a rutile blue so it may not be the cobalt issue. I noticed your clay body is for cone 10, but you are glazing to cone 5/6(?). For functional wares, you might want to consider a cone 6 clay body. At cone 6, your clay is likely under-fired and not properly vitrified.

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Hi All:

 

Thank you for your responses. I haven't used this exact combo but I have used the Rutile paint on glaze with this clay with a lot of success. This situation has occurred when I switched to the powdered/dip glaze. After reaching out to Amaco they suggested that instead of doing two layers (dip, let dry, dip, let dry) - that I'd be better off with dipping once and holding it in the glaze longer to achieve a better result. They suggested that the 2nd layer didn't grip the clay body well enough because it was over the first layer.

 

The firing was a fairly slow Cone 6. About 8.5 hrs to fire. The insides of the ware were for the most part unaffected - the outsides we definitely worse. Pieces from all different levels in the kilns were affected. There didn't seem to be much a difference between higher vs lower shelves.

 

There was no noticeable cracking in the glaze and hands were clean prior to glazing.

 

Thanks for everyone's feedback!

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How long were you letting the first dip dry before doing the second dip? If you let it dry too much, the second dip will make the first dip lose its grip on the clay. Also, applying glaze thick can totally saturate the walls of the pot if they are thin, which can also cause adhesion problems.

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I have used the Rutile paint on glaze with this clay with a lot of success.   by "paint on" you mean premixed?

 

This situation has occurred when I switched to the powdered/dip glaze   same glaze as above except in dry mix?

Been following this thread for awhile.... the only difference I have noted is switching from pre-mix to dry-mix. So that makes me question how you are mixing? Sieved? Water to dry mix? viscosity?  etc.

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I have used the Rutile paint on glaze with this clay with a lot of success.   by "paint on" you mean premixed?

 

This situation has occurred when I switched to the powdered/dip glaze   same glaze as above except in dry mix?

Been following this thread for awhile.... the only difference I have noted is switching from pre-mix to dry-mix. So that makes me question how you are mixing? Sieved? Water to dry mix? viscosity?  etc.

 

 

There has been a lot of discussion on the Amaco Potters Choice Facebook page about the differences between pre-mix and dry.  Seems like the pre-mix is formulated for brushing, and the dry for dipping.

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Chilly:

 

Does Amaco detail that information on their products, or website? I do not deal with premix glazes rather wet or dry: so I do not comment alot about them. In trying to find some info about them for a friend: I was shocked by the stunning lack of information given.

 

Nerd

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Chilly:

 

Does Amaco detail that information on their products, or website? I do not deal with premix glazes rather wet or dry: so I do not comment alot about them. In trying to find some info about them for a friend: I was shocked by the stunning lack of information given.

 

Nerd

 

 

Hmmmmmm.  Can't now find the Facebook group.  I unjoined it a while back as I was fed up with people flouting the rules, but there were lots of comments about the differences (real or imagined) between pre and dry.

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Chilly:

 

Does Amaco detail that information on their products, or website? I do not deal with premix glazes rather wet or dry: so I do not comment alot about them. In trying to find some info about them for a friend: I was shocked by the stunning lack of information given.

 

Nerd

 

This link https://s3.amazonaws.com/amacobrent/home/deploy/amaco/releases/20160108030925/public/ckeditor_assets/attachments/914/pc_buckets_combo_doc_1-18-16.pdf page 2 does state that "Because dipping glazes don’t have the binder that brushing glazes have...."

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I think binders are added not to bind glaze to pot but to make the glaze more painterly, my word there.

Because of the double dip I think the thickness of glaze layers, linked with state of dryness between layers caused this

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I think binders are added not to bind glaze to pot but to make the glaze more painterly, my word there.

Because of the double dip I think the thickness of glaze layers, linked with state of dryness between layers caused this

 

Exactly

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