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First Test Pieces - Glaze Not Glossy


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#1 Melissa M.

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Posted 23 August 2013 - 08:34 AM

I have fired my first pieces, and I don't think they look glossy enough. 

 

I used various clay bodies (Cone 5/6), underglazed the greenware with Amaco LUGs, then applied Amaco Sahara High Fire HF9 clear glaze to the bisque. It was brushed on, and I applied three coats. (They are miniatures, so I find brushing is much easier than dipping.) The pieces were then fired to Cone 5. (Bisque fired to Cone 04.)

 

None of the pieces turned out as glossy as I think they should be. I'm not certain if they should be glossier or not. It's difficult to tell. I have attached a photo of one of the pieces. Hopefully, you guys can tell if it looks glossy enough.

 

If it is not as glossy as it should be, what steps would I take to correct this in future firings? Wouldn't an additional coat of clear glaze possibly cause crazing?

 

Thanks!

Melissa

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#2 atanzey

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Posted 23 August 2013 - 09:05 AM

It does look satin instead of high gloss.  But I find the result very pleasing on that form.  For me, glossier might not be as nice. 

 

But as to the 'why' - is HF9 indicating Cone 9?  And you went to Cone 5?  It seems that would be underfired, which would usually result in an incomplete melt.

 

Alice



#3 Melissa M.

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Posted 23 August 2013 - 09:21 AM

It does look satin instead of high gloss.  But I find the result very pleasing on that form.  For me, glossier might not be as nice. 

 

But as to the 'why' - is HF9 indicating Cone 9?  And you went to Cone 5?  It seems that would be underfired, which would usually result in an incomplete melt.

 

Alice

Thanks, Alice. :) 

 

No, sorry, the clear glaze (HF9) is a Cone 5-6 glaze. 



#4 bciskepottery

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Posted 23 August 2013 - 09:32 AM

Are you sure you reached ^5 or ^6 in firing? Matt could be caused by underfiring.

#5 Melissa M.

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Posted 23 August 2013 - 09:41 AM

Are you sure you reached ^5 or ^6 in firing? Matt could be caused by underfiring.

Actually, I'm not certain. The Cone 4 witness cone did overfire. However, the Cone 5 witness cone underfired, but I thought it may have been because it was close to the front (door) of the kiln. But, now that I think about it, all the pieces turned out like this, so perhaps it did underfire??

 

Maybe I need to try a Cone 6 firing next time?



#6 oldlady

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Posted 23 August 2013 - 09:49 AM

like your little bird.  what size is it?


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#7 Melissa M.

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Posted 23 August 2013 - 09:56 AM

like your little bird.  what size is it?

Thanks! It's about 3/4" long. :)



#8 oldlady

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Posted 23 August 2013 - 10:37 AM

that is much smaller than i imagined.  what do you do with it?


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#9 Denice

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Posted 23 August 2013 - 10:47 AM

I would refire to C6 and try cooling it faster.  Denice



#10 Melissa M.

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Posted 23 August 2013 - 11:00 AM

that is much smaller than i imagined.  what do you do with it?

It's just a little collectible decorative piece. :) I currently sell my pieces, but they are made with polymer clay and acrylics. So, I am now starting to create my designs in ceramic. 



#11 Melissa M.

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Posted 23 August 2013 - 11:15 AM

I would refire to C6 and try cooling it faster.  Denice

Thanks for your advice, Denice. 

 

The kiln actually cools fairly quickly on it's own. (It's a small test kiln.) I'm worried that cooling any faster may cause crazing.  :unsure:



#12 Bob Coyle

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Posted 23 August 2013 - 01:28 PM

I have a small test kiln that loses heat pretty fast. I bought enough 1 inch Kaowool blanket to put a couple of layers across the top of the kiln. This did slow down the heat loss. It also helped improve the ramp up to cone 6.



#13 Marcia Selsor

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Posted 24 August 2013 - 06:59 AM

I agree with the geezer. I put a blanket of fiber on my test kiln. Also I use one higher cone than the glaze because it fires fast and no soaking. I figure that helps with the heat work.
I get pretty accurate tests.
I like the satin matt on your piece. It looks like Van Biggle's satin matt.

Marcia

#14 clay lover

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Posted 24 August 2013 - 07:35 AM

VERY cute little fellow. I like!

Agree, under fired. What the kiln says it did, what you told it to do and what it actually did can often not match up. Use lots of cone, 3 for each shelf in different positions.

#15 OffCenter

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Posted 24 August 2013 - 09:33 AM

I have a small test kiln that loses heat pretty fast. I bought enough 1 inch Kaowool blanket to put a couple of layers across the top of the kiln. This did slow down the heat loss. It also helped improve the ramp up to cone 6.

 

It seems common sense to assume that more heat is escaping through the top of the kiln, but that is not the case. All else being equal, just as much heat is escaping through the sides and bottom so it would help just as much to put a layer of kaowool under the kiln as on top of it.

 

Jim


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#16 Melissa M.

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Posted 24 August 2013 - 05:40 PM

Thanks for weighing in, everyone. :) 

 

Looks like I need to try Cone 6. 

 

I'm a little confused regarding the cooling though. One person suggested I cool faster, while others are suggesting ways to cool slower (with the fiber blanket).  :unsure:



#17 Mark C.

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Posted 24 August 2013 - 06:06 PM

Cooling slowly devlopes the glazes better just as firing slowly does. I'd wrap the whole baby kiln to slow it down.Sounds like its plenty small and easy to do.

mark


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#18 OffCenter

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Posted 24 August 2013 - 06:20 PM

Thanks for weighing in, everyone. :)

 

Looks like I need to try Cone 6. 

 

I'm a little confused regarding the cooling though. One person suggested I cool faster, while others are suggesting ways to cool slower (with the fiber blanket).  :unsure:

 

It always depends on the glaze. The person who suggested cooling faster is probably right if you're trying to get glossy clear. For some glazes, especially mattes, slow cooling is better. For some, super slow cooling is best. Some potters use incredibly complicated holds and ramp downs for cooling saturated iron glazes. The only way to find out what works best is by testing.

 

Jim


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#19 Pres

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Posted 25 August 2013 - 02:13 PM

I used to use a lot of the Amaco HF glazes, along with other commercial ^5-6 glazes.  The HF series is very temperamental at anywhere under cone 5 and are usually best in all respects at cone 6.


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#20 Chris Campbell

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Posted 27 August 2013 - 11:58 AM

I'm reading this because you have the look I want to get ... I love that satin finish so I am going to try under firing the commercial clear and hope it happens.


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