"Iron Wire and Golden Thread" Effect

[Ben xyz]

Anyone tried this double crackle effect with a Guan ware type glaze (also described as Ge ware, 13th/14th century AD - China)?

[Min]

I love how curious you are about so many different techniques and styles! Stain the initial primary crazing then leave the pot for the secondary craze lines to develop unstained.

[PeterH]

I remember seeing several "iron wire and golden thread" pots in the Percival David museum years ago, and they formed a lasting impression.

A couple of weeks ago I noticed that a crackle pot that I probably made in the 1980s had developed a significant number secondary cracks. But these cracks only visible when looking hard from a foot or so.  So I've been wondering if I should stain these secondary cracks with a brown "Indian ink". Although I'm not certain that the primary cracks are bold enough to give a good end result. 

PS From p585 of Ceramic Technology by Rose Kerr and Nigel Wood (Volume 5 part 12 of https://en.wikipedia.org/wiki/Science_and_Civilisation_in_China)

Perhaps the best evidence for the contemporary appreciation of crazing in Kuan and Ko ware is the occasional practice of staining the major glaze-crackle with an intense black pigment to provide a network of fine black lines on a smooth light ground. By necessity, this would have happened soon after the firing, and most probably when the wares were still hot from the kiln, when the craze lines were relatively open. Ceramics can continue to craze for days, or even for years, after firing,and this secondary crazing system often appears as a finer network on Kuan wares, between the major crackle lines. This secondary crazing is often stained a lighter colour, perhaps deliberately or perhaps simply through use. These two crazing systems supplied the celebrated "gold thread and iron wire" effect, so often admired in Kuan and Ko wares.  How the fashion for staining the crackle began is not known,but one possibility is that it was first used as a `rescue' process, designed to improve the appearance of accidentally oxidised pieces.

[Ben xyz]

On 9/21/2023 at 8:46 PM, Min said:

I love how curious you are about so many different techniques and styles! Stain the initial primary crazing then leave the pot for the secondary craze lines to develop unstained.

Likely made my folks crazy with all my questions growing up! Thanks Min and Peter for the input. Had read somewhere (possibly here) about using an Underglaze the same way as India ink on the cracks and firing again. Need to try. I like the subtle depth that occurs when using two colors at two different times.

Edited September 23, 2023 by Ben xyz
Clarification

[PeterH]

8 hours ago, Ben xyz said:

Likely made my folks crazy when growing up! Thanks Min and Peter for the input. Had read somewhere (possibly here) about using an Underglaze the same way as India ink on the cracks and firing again. Need to try. I like the subtle depth that occurs when using two colors at two different times.

1) Wouldn't you need either a liquid or a very fine powder to get into the cracks? I've seen it suggested that the pigments in tube watercolours can fit the bill. One based on iron oxide seems an obvious starting point. I'd be inclined look for one where the manufacturers adverts show it dilutes well.

.. or if you have a ball-mill.

2) I've also seen suggestions about using a non crazing glaze. First glaze firing to lower than maturity, which apparently can leave cracks. Stain with heat-proof pigment such as above.  Second glaze firing to maturity, (partially?) sealing the glaze.

From Ceramic Techniques, Pravoslav Rada p73
Crackles can be produced artificially by heating the pot and then sprinkling cold water on the surface. After crackle staining and refiring the coloured crackle pattern will remain coated with perfect glaze. The same effect can be achieved if a normal glaze is under-fired by 80-100C. Crackles produced by under-firing are then stained and the pot refired once again to the correct temperature.
... but getting a related primary and secondary crackle requires the secondary crackle to form under the influence of the primary crackle. Maybe you could apply the heat & cold water treatment twice?

PS Re "inking" warm/hot pots (presumably <100C) to give more pronounced staining. Would the small temperature differences make much difference to the width of the crack? Maybe it would influence the viscosity of the ink more?

 

PPS Haven't used them for years, but Kremer Pigments sell all sorts of exotic stuff. IIRC they have both  European and  American sites.
https://shop.kremerpigments.com/us/

They have lots of iron oxide pigments, including:

From the data sheets:
Predominant particle size approx.. 5.8 μm
... another iron oxide pigment was Sieve residue (0.045-mm-sieve) (%) max 0.1 (0.045mm = 45 μm)

 

Edited September 23, 2023 by PeterH

[Callie Beller Diesel]

Use India ink on the larger crackles, and soak them in tea for the secondary pattern. Apply the ink when they’re freshly crazed out of the kiln, and then do the soak a few days later. 

[Ben xyz]

On another but related note, have noticed some people feel such cracking is not food safe, though other cultures revere such cracking effect (teacups, etc).
Perhaps one could stain the cracks (with something that would not burn out) and add a clear glaze on top and fire again if hygiene is an issue (though the ongoing cracking underneath may mess with the clear on top...or not).

[PeterH]

14 hours ago, Ben xyz said:

On another but related note, have noticed some people feel such cracking is not food safe, though other cultures revere such cracking effect (teacups, etc).
Perhaps one could stain the cracks (with something that would not burn out) and add a clear glaze on top and fire again if hygiene is an issue (though the ongoing cracking underneath may mess with the clear on top...or not).

My understanding that adding a glaze on top of a non-porous surface is a non-trivial task.

Two area where this is commonly practised are  bone-china and china-painting: both apply a low-fire glaze over a non-porous high-fire surface.
 

... note the quote
Since the porcelain has zero porosity, getting a glaze to stick and dry on it is not easy, the process needed goes well beyond what a normal potter would be willing to do.

China-painting relies on a wide range of "painterly" mediums, and is usually about applying painted decoration rather than flat-films. Of course, china-paints tend to be both opaque and non-food-safe -- I'm just talking about the technology.
Painting with Overglazes
https://ceramicartsnetwork.org/docs/default-source/uploadedfiles/wp-content/uploads/2018/02/chinapaintchapter5.pdf
Oils and Mediums
http://www.porcelainpainters.com/mediums.htm

If you want to pursue to idea of glaze-on-glaze to render crackle finishes food-safe it might be better to start a new thread on the topic.

[Min]

20 hours ago, Ben xyz said:

On another but related note, have noticed some people feel such cracking is not food safe, though other cultures revere such cracking effect (teacups, etc).
Perhaps one could stain the cracks (with something that would not burn out) and add a clear glaze on top and fire again if hygiene is an issue (though the ongoing cracking underneath may mess with the clear on top...or not).

In addition to what Tom said the covering glaze would be somewhat blended with the crazed base glaze when they are fired.

On a side note, I have some pots I use daily at home that are vitrified but partly unglazed on the outside. When testing this clay I wanted to make sure it didn't stain from everyday use where it is unglazed. I soaked the fired samples in beetroot water, strong tea and coffee and sumi ink. Nothing stained it and years later the pots still look pristine. Takeaway from this (for the Iron Wire and Golden Thread) would be to use a body that doesn't totally vitrify if you use a stain that isn't fired on like a china paint.

[Kelly in AK]

On another side note, verging into off topic territory, yet not, is the copper red crackle that can happen on re-firing. I didn’t take pictures of my own pots this happened with, but I assure you from experience it happens. Crazed copper red glaze can go red in the craze lines. I believe reduction cooling or “strike firing” is a purposeful way to make it happen. I found a picture from Christie’s auction house that shows it.