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cstovin

Glazed interior of pots and Raku firinf

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Hello all,

 

I haven't been able to experiment with this yet, but I wanted to hear some opinions, experiences, advice, etc from anyone that could offer any....I have some larger vases that I want to RAKU fire, but I want them also to be usable. I know a plastic liner can be used on the inside to hold water, but I wanted to glaze the inside when they were still greenwear and just fire to cone 06 (skip firing to cone 04) but my question is:

 

 

WHen you use regular clear glaze for the interior of vases it is typically lower temp than RAKU; can I glaze the inside of the pots, then raise them to the needed temp to RAKU, perform the RAKU firing and do that at the temps needed (1500 - 1800), without that damaging the interior glaze? I guess what I am asking is that the RAKU firing is higher temp, so I don't know what that will do to the already glazed interior of my pot?

 

 

Any experiences with this? Suggestions? Ideas? I really want to glaze the inside of a few of these, but not sure that it will work, can't really afford just to go willy-nilly and experiment at will....any advice is GREATLY appreciated!

 

thank you all

 

Charlene Stovin

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Hello all,

 

I haven't been able to experiment with this yet, but I wanted to hear some opinions, experiences, advice, etc from anyone that could offer any....I have some larger vases that I want to RAKU fire, but I want them also to be usable. I know a plastic liner can be used on the inside to hold water, but I wanted to glaze the inside when they were still greenwear and just fire to cone 06 (skip firing to cone 04) but my question is:

 

 

WHen you use regular clear glaze for the interior of vases it is typically lower temp than RAKU; can I glaze the inside of the pots, then raise them to the needed temp to RAKU, perform the RAKU firing and do that at the temps needed (1500 - 1800), without that damaging the interior glaze? I guess what I am asking is that the RAKU firing is higher temp, so I don't know what that will do to the already glazed interior of my pot?

 

 

Any experiences with this? Suggestions? Ideas? I really want to glaze the inside of a few of these, but not sure that it will work, can't really afford just to go willy-nilly and experiment at will....any advice is GREATLY appreciated!

 

thank you all

 

Charlene Stovin

 

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I thought most raku firings were around Cone 06? And many clear glazes are at Cone 05 which is hotter.

But, that aside I would not put water in any raku vase or tell others they could ... Water has an inflexible way of finding a route out of the smallest crack and onto your best wooden tabletop. :D

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Mnay people have fired bright commercial glazes prior to raku firing. As Chris says many use ^06 for Raku. I would glaze the pieces in a separate firing because the interiors of raku pieces often ten to be immature or not fired hot enough because of the rapid firing. Better to fire them first, then raku.

 

 

 

Marcia

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Hi Marcia - That is what I was wondering if I could do - fire them first with glazing the interior, then refire them for Raku; realizing that I might weaken them by firing them twice, I would need to be careful, but I wondered if it could be done? But, that is exactly what I wanted to do - clear glaze the inside, fire it - then raku glaze the exterior and head off to the Raku kiln...

thanks for the input

Charlene

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Yes, you can do that ... I have fired the interiors all the way up to Cone 5 first, then raku fired the exteriors ... my caution would lie in expecting them to safely hold water once you are done.

 

As a note ... The clay I fired to Cone 5 was a Cone 10 clay so I was not firing it to maturity. Right or wrong (?)I thought I needed to leave some openness in the clay body to minimize stress breaks during quick reduction.

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Thanks Chris - I guess point taken; I was thinking for some reason that if I glazed the insides of the pots they might sell better for people that don't understand RAKU? do you ever have a problem selling larger (or any) vases that are not water tight?

 

I am pretty new to RAKU and love it, but just wonder if/what people's reactions are to vases that they can't use, or have to use with dry flowers, or with plastic liners rather than like a traditional vase?

 

Advice is appreciated, maybe I am doing that extra step for nothing, or worrying for nothing and shouldn't worry about glazing the inside?

Charlene

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While the glaze may mature and glass over just fine, the rapid cooling of the raku process will cause it to craze. For example, the White Crackle type glazes used in raku are simply clear glazes, and the rapid cooling causes them to crackle (craze), and the carbon is trapped in the clay, highlighting the crackle pattern. Most raku clays mature at cone 10 or thereabouts. So even if you pre-fire to cone 5, you'll have a clay with an absorption rate that is high enough that it will weep if the glaze on it is crazed. If you were to raku fire a pot that had been fired to full maturation and vitrification, it would most likely crack during the raku firing.

 

Go with a plastic liner.

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You can go with a silicon liner much like coating dry flies for fly fishing. Annie's Mudshop in Cincinnati sold one called Water Guard or something like that. It was developed for sealing raku pieces to be water proof.

I would recommend just firing your glaze to about ^04 or ^05. Unless you have a very refractory ^5 body, you run the risk of cracking it when you retire in a fast raku firing. It depends...as always. Chris is very experienced but I don't know what clay she was using. And I don't like contradicting what she says. If she did it by underfiring a ^10 clay to ^5 sufficient to keep it open somewhat that is great, but your clay may not do it.

 

 

Marcia

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You can go with a silicon liner much like coating dry flies for fly fishing. Annie's Mudshop in Cincinnati sold one called Water Guard or something like that. It was developed for sealing raku pieces to be water proof.

I would recommend just firing your glaze to about ^04 or ^05. Unless you have a very refractory ^5 body, you run the risk of cracking it when you retire in a fast raku firing. It depends...as always. Chris is very experienced but I don't know what clay she was using. And I don't like contradicting what she says. If she did it by underfiring a ^10 clay to ^5 sufficient to keep it open somewhat that is great, but your clay may not do it.

 

 

Marcia

 

 

 

Thanks all for the input....it all makes sense - maybe just stick with the plastic liner. I think maybe I am making this too hard and too time consuming; I guess if they like the pot, they will buy the pot glazed interior or not.....when I first found out they were decorative only my reaction was a little "bummed" just because I thought that would limit the appreciation.....I have also learned a LOT since then, and love the RAKU, and know more now, and appreciate more now.....but john Q Public sometimes doesn't care to be educated on WHY things aren't glazed or usable.....so was just curious what other people do... to glaze or not to glaze....thanks all!

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I have been working with raku for many years, and agree with Chris that most buyers are interested in the unusual glazes that are used in raku. Make your pots decorative in shape or surface design (under glazes) (metallic glints) and it the pots will be the showcase, not what it could hold. I primarily make fruit bowls, small necked bottles or vases, and wall decor.

 

I use Coleman Raku clay which has a firing range of cone 06 to cone 10. Have never fired it above cone 6. I have fired a solid glaze (cone 06 or 05--the same temp I achieve for raku) inside the pot and then, later, raku fired the outside. As has been noted, the thermal shock of raku firing could possibly craze the interior glaze. When I did this type of glazing, rather than dousing the work in water I'd leave it in the post-firing reduction until it was cool enough to handle with bare hands--sometimes overnight. To the buyer, I'd point out that the work is purely decorative, and if they insisted on using it for holding water and flowers, they'd best use a saucer of some sort under it or kiss their wood furniture goodbye. If you use a sealer on the inside, make sure it comes all the way up to the neck of your pots.

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