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PeterH

Member Since 28 Apr 2013
Offline Last Active Today, 07:20 PM
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Posts I've Made

In Topic: Sugar/candy Raku

14 April 2014 - 03:14 PM

Thanks, but the sugar raku I'm interested in is a variant of the 2-part naked raku process, in
which the refractory 1st coat contains sugar. Normally 2-part naked raku leaves black "crackle"
lines. On the other hand sugar raku -- from the few photos I've seen -- leaves black patches,
often with some sort of halo effect.

 

Overall effect is something like the left-hand pot in

http://tinyurl.com/pzubofy

 

Every few years I'd try again using the normal 2-part naked raku process, and got a really ugly

pot in a mixture of black and charcoal greys.

 

Last time I tried cooling it in oxidation, with more interesting results.

 

Firstly tried quenching as soon as it came out of the kiln.
Attached File  quench_350.JPG   47.33KB   2 downloads

 

Then letting it air cool sitting on a brick

Attached File  air_350.JPG   57.65KB   3 downloads

Different, but nothing like the pictures I'd seen.

 

Finally I tried to repeat the second experiment, but botched it. I put it on short damp grass to cool, and

it had fallen on its side by the time I got back.

Attached File  grass_350.JPG   59.03KB   1 downloads

Obviously it had seen a mixture of oxidation and reduction.

 

So, I'm interested to know how other people cool their sugar raku.

 

Regards, Peter

 

For completeness.

Fired somewhere in the range 1030-1050C.

Slip was china clay 3, flint 2, sugar 2 by volume. I also tried a 3:2:1 mix but it was rather faint.

 


In Topic: Shinny Sparkles In A Glaze

14 April 2014 - 10:38 AM

You may also be interested in some of the thread

http://cone6pots.nin...source=activity

... I would start with page 3


In Topic: Shinny Sparkles In A Glaze

14 April 2014 - 10:32 AM

As you are using a Crystaltex glaze, I assume that you know that you can buy the "crystals" separately

http://www.bigcerami...e-crystals.html

... although they don't look very sparkly to me.

 

I'm still intrigued by your picture of Crystalline Ultramarine with the copper sparklies. Have you used this glaze,

just seen a picture? Can you give me any pointer to it, or say where your picture came from?

 

On a negative note, look at this advertising picture of a commercial Copper Aventurine

http://www.bathpotte...nt-el-121/p3874

... AFAIK good sparkles require carefully controlled cooling cycles


In Topic: Shinny Sparkles In A Glaze

13 April 2014 - 05:34 PM

Just a ranging shot to fully understand the question.

 

When you say shiny sparkles, and talk about crystalline glazes,  I immediately think of aventurines.
http://www.qualicer....df/0062315e.pdf
http://community.cer...enturine-glaze/


Which I believe to be quite tricky, and would expect redox issues would make copper aventurines
even trickier.

This picture of a copper aventurine glass clearly shows the attractions
http://en.wikipedia....nturinglas).jpg
... and the associated wiki page indicates some of the difficulties in it's production (and a glass in its tank --
unlike a glaze in a kiln -- is more or less isolated from the environmental redox).
http://en.wikipedia....tone_(gemstone)

The wiki entry suggests to me that the matrix of an aventurine glaze will always be dark, as it will still contain

some precursor oxide of the crystals (and they always seem to involve the transition elements, which have

highly coloured ions).

Your request for "just the copper sparklies" suggests that you are after a clear copper aventurine. If so, you

may be out of luck.

 

Regards, Peter

 

BTW I'm not familiar with Crystalline Ultramarine. Do you have a reference, which might give a clue as to the

mechanism behind the sparkles.

 


In Topic: Ftl Error Message

13 April 2014 - 01:15 PM

Looks like good advice from GEP. Here is a Paragon Sentry troubleshooter (not necessarily you model)

http://www.paragonwe...ubleshooter.pdf

... see p14 for

 

PROBLEM FTL / Firing Too Long
The temperature change is less than 27°F/15°C per hour and
the firing time is four hours longer than the current segment
was programmed to fire. This message can appear during
heating-up or cooling-down segments.

 

Was the firing too slow?
If FLT  appears well below the target temperature during a
heating-up segment, such as 1000°F for an 1800°F firing, you
probably have a burned out element or relay. See “Kiln fires
too slowly or will not reach temperature,” page 6.
 
Check for worn or burned out elements, defective relays, low
voltage and defective thermocouple.
 
 
Did FTL appear during a controlled
cooling?
If FLT appears during a cooling segment, it is usually be-
cause the segment was programmed to cool faster than the
kiln’s natural cooling ability. To avoid getting the FLT mes-
sage, program a slower cooling rate.