Throwing Caution to the Wind...

Ok guys and gals thought I would do something a little different on the pot forum and share a glaze recipe
What I would really like and if my potting comrades are up for it is to use this glaze recipe as a base glaze and for others to add oxides etc and fire the altered base glaze and show the results whilst also sharing the "extra" ingredients. I did tell Rob I would send him this glaze as it is a reduction glaze and he has a new gas kiln and then thought we can all benefit from this.
Anyway here is the recipe....

Satin / Matt White Crackle 1260 - 1300 degrees centigrade

Potash Feldspar 50
China Clay 23
Dolomite 20
Quartz 4
Bone Ash 3

When I have fired the glaze I have started reduction about 950 c and not soaked the kiln at top temp, which for me was 1280 c.

Here are the results of the base glaze



So come on you crazy potters lets see if we can come up with something interesting, different, sexy even and share it with each other

All the best

Andy

Andy,

I'll work with you on this one.

A couple of questions for you:

When you say "China Clay" are you referring to kaolin? If so, is there any specific grade you use.
Grolleg, Tile-6, and Edgars Plastic Kaolin (EPK) are the most common available to me.

For the quartz component, what mesh size are you using? I have 200 and 325 mesh on hand.

Cheers,
Paul

Hi Andy,

beautiful pots.

With crackled glazes I have not tried, because in Germany they are not as well suited for bonsai pots, as they are not very frost resistant. I've seen a lot of pots, which are even years later broke. This is a big problem.

Unfortunately, my technical English is absolutely bad, so I can not tell you exactly.

An english translation can be found here:
http://www.bonsaipots.net/index.php?page=frost-resistant-pots

Nevertheless, I wish you a lot of fun experimenting.

Regards
Peter

Hi Paul

China Clay is what it is sold as over here in the UK, but yes Kaolin is the same thing but I dont use any particular grade as when the glaze is mixed together I use a 100 mesh sieve to sieve the whole glaze through.

Again the quartz component that I buy does not say what mesh or grade it is, it is very fine though and either grade you have I should imagine will be fine.

Looking forward to the results and the extra ingredients

Hi Peter

Thanks for your knowledge and expertise. So far, fingers crossed, I have not had a problem with a crackle glaze through a frosty winter. I have a large cascade pot I made fired to 1280 that has been in my garden over the bad winter we have had here in the UK for over the past 20 years and all has been ok. That's not to say that it won't happen in the future. I can understand the reason why this may happen and many thanks for posting your article for us all to read.

Regards to you both

Andy

how would this glaze react in oxidation rather than reduction?

I'll give it a try

Hi Guys, as an aside, the cracle will vary on differing claybodies. It is low in Silica, reason for cracle. So. if you don't get just what you want. just do a line blend with the Silica as the variable. I've used 200 & 325 mesh Silica with only magnified differences.
Wood

Hi Kitoi

Please give it a go and show us the results. Would be nice to see if there is any difference in an oxidised firing

Kind regards

Andy

Andy,
I had a pint of your recipe mixed up for me at glazemixers (dot) com and
added a bit of tourquoise mason stain. It arrived today and I will put it on some
bisque and post results. (I named it StoneMonkey Matt Crackle)
If I had any guts I would have added the chartruese stain. Still might.

Its a private recipe until tested then can be put in community recipes on that site, btw.

Thanks for the inspiration,

Judy

Hi Judy

Excellent Idea! Turquoise stain

Really looking forward to seeing the results

Hi Gary

Good point about the clay body. The clay body I have in the picture is a grogged white stoneware. Here in the UK, well from my clay suppliers, the grog size is not known just in case anybody asks

Kind regards

Andy

Andy,

I was able to prepare a test batch of the base mix last week and got two test tiles in the load I fired on Friday.

As you can see from the attached photo it was a disappointment.

The tile on the right is a white stoneware. The tile on the left is porcelain.



Not quite what we had in mind.

Here's the breakdown of what I used

G-200 (potash feldspar)
Grolleg (china clay)
Dolomite
Quartz (325 mesh)
Bone Ash (synthetic)

These were mixed in the quantities you listed. The tiles were dipped three times to insure a good coating of glaze.

I fire to cone 10 (2385 deg. f.) in a gas, reduction kiln. I do a body reduction at cone 08 and a glaze reduction at cone 9.

What are your thoughts?

Regards,
Paul

Interesting Paul, any idea why it reacted that way?

Mixed a batch myself, using kaolin for the clay component. Will fire a couple of tiles this weekend.

Paul, if you look at the roll at the bottom of the first tile you will see crazing. Crackle, like Andy's glaze, is the same thing only in magnitude. The question is what degree do you want. most functional glazes avoid this, considered a fault but decorative glazes are different and this "crazing" can be amplified to a degree that suits your taste. Just looking at the tile, my guess is, fired tooo hot on a smooth body. Try a cooler spot in the kiln. If that is not an option then do a line blend reducing the silica. It might be that it has to be run through a glaze program and match Andy's with your materials.
Wood

Andy,

You know, with all things being the same in the actual recipe and firing temp, (which by now has already been altered) you may want to let us know of your claybody shrinkage too. It can be a big factor in crazing. Of course you know this already, but it would be good to count this out first....

Real busy getting stock up now and waiting for gas hook up to the shed. I will test next month?

Thanks,
Rob

Hello Andy

I very nice idea to share a recipe and compare the results!
I only have an electric kiln so your recipe cant be used with it but I have done the first bisque-firings for a long time now and will also do some testtiles in the glazefiring. There is a crackle glaze with it and I will show the results here.

Kind regards
Klaudia

Paul

Thanks for posting the results. A HUGE difference to what came from my firing and not very nice either, looks a little like a Celadon Glaze, but not what I was expecting. I usually dip three times to get a good glaze coating also.

Kitoi

Look forward to seeing your results after firing.

Rob

The shrinkage on this particular clay body is quiet low as it has a high grog content. The shrink rate is about 12% if that helps. The thing is I use it on other stone ware clay bodies with a higher shrink rate and it still come sout crackled and ok. The only clay body I have tried it on and it did not crackle was on a terracotta body.

Klaudia

Look forward to seeing the results

Regards to you all and thanks for your input and firing results

Andy

Stone Monkey wrote:Paul
Thanks for posting the results. A HUGE difference to what came from my firing and not very nice either, looks a little like a Celadon Glaze, but not what I was expecting. I usually dip three times to get a good glaze coating also.
Andy

My pleasure Andy, I appreciate your willingness to share.

This is pretty much what I expected based on the glaze formula.

I will be firing again in two weeks so I will make some adjustments and see what comes of it.

Cheers,
Paul

kitoi wrote:Interesting Paul, any idea why it reacted that way?

Mixed a batch myself, using kaolin for the clay component. Will fire a couple of tiles this weekend.

Hi Keith,

It is mainly due to differences in the raw materials. Remember, we are dealing with components that are mined and refined in different location. The physical and chemical make-up of the materials is not identical. That is why I asked Andy about some of the components that he listed. Not all glaze formulas transport readily from one location to another. Especially ones like this.

I look forward to seeing the results of you tests.

Paul

GaryWood wrote:Paul, if you look at the roll at the bottom of the first tile you will see crazing. Crackle, like Andy's glaze, is the same thing only in magnitude. The question is what degree do you want. most functional glazes avoid this, considered a fault but decorative glazes are different and this "crazing" can be amplified to a degree that suits your taste.

Gary,

I believe the crazing on the porcelain test tile is mainly due to the thickness of the glaze at that location. This is a problem that I have seen before on over-glazed pieces. This glaze (my mixture) has a high degree of movement as evidenced by the runs on both test tiles.

GaryWood wrote:Just looking at the tile, my guess is, fired tooo hot on a smooth body. Try a cooler spot in the kiln.

This could be a contributing factor to the differences. But what in particular would lead you to this conclusion? Based on Andy's numbers it appears that he is firing to at least cone 9 and his base formula appears to be capable of being fired to cone 10.

GaryWood wrote:If that is not an option then do a line blend reducing the silica. It might be that it has to be run through a glaze program and match Andy's with your materials.

I plan on tweaking the formula a bit. I have tested a number of cone 10 crackle glazes and have found that the only ones that work reliable for me are the ones without any silica at all. In addition, I am going to change the kaolin component to EPK.

Regards,
Paul

chartruese crackle? Andy, here is the juice glass size pot
up close there is some crackle which could be augmented
by the dishwasher I bet...





(I just converted it to a pot in bisque stage in order to test the crackle glaze)

Thanks for looking...

Judy

Am just learning about photog, etc. but thought this king louis box showed off the pot well.

Dear Andy

In Your topic , its all about glaze/addics/ways to fire to get a crackled surface.
You know i love Your white/fat crackle , but i could not get it out of my kiln.

So ...... i did something else to get a crackled look
* Made it in the claybody before drying and glazing.
* combined the 3 glazes that i knew would work melting into eachother
in the heating and work the other way in the cooling down.
This is one of the little pots .

Dear Judy
The king louis box is gorgeous with Your pot !!!!
You could use a different background to get a stronger presentation.
Keep up the female approch , its wonderfull !

Kind regards
Morea

Thank you for your encouragement, Morea!

Your pot looks rich and warm somewhat like a crusty loaf of french bread. Oh, I must be hungry, lol

The little chartruese pot has wonderful texture and variation of matt and some bits of glossiness
but not THAT green in a room. Am sure the red box made it look that way a bit.

The glaze was brushed on THICK.

The clay is Bravo Buff (^6 - 10).

I need advice on shape and aesthetics for my bigger pots and will find a thread for that.

My best Regards to All,
Thanks to Fiona and Morea for making me feel welcome
and to Andy and Dale and Mike for ignoring my confusions...

Judy

Hi Judy

I like the result, nice colour I know you added a commercial stain to the base glaze and I think it has been a pleasing result. What percentage of stain did you add? This colour would suit a number of trees, quince, azalea etc and accent plants. I am sure your going to use this glaze on future pots. Really pleased to see a positive result and thanks for testing and showing.

I will show my addition soon as I have been a little sidelined of late.

Hi Morea

Love this pot!!! I agree with Judy warm toasted bread, YUM!!



Regards to you both

Andy

base fired to 2300f in oxidation (electric) and normal cool down


base with 4g copper carb and 3g nickle


a closer look


With the additives the glaze has a look and feel to it and it more satin than the base.

Andy,

The downside of Mason Stain is that it isn't cheap. But, For the pursuit of just the right pot, it might be worth it.

I mixed dry two mason stains, Cerdec Yellow encapsulated (whole little plastic container which says 1 oz) and a small amt
of French Green about 1 and 1/2 teaspoons. Now about a tablespoon of that mixture was added to about 1/2 cup of the stonemonkey mattcrackle
premixed liquid. I also experimented with adding more of the french green in separate batch and it was unremarkable as a
color for bonsai. (Color of clay is a big factor here) ONLY the bravo buff (light greyish stoneware) was desirable.
The other clays look like pea soup on the outside of the pot...

If you are looking for this color here is a place to start. I will try the french green in other combos and if pretty will post.

Sorry about the increments. I have to switch to weights from volume in metric but my mind thinks in cooking terms.
Judy

ANDY,
Please note that the original mixed glaze also had in it by percent of the whole pint: Mason Stain 6364 .50 %

Sorry for the confusion - I just remembered it...

Judy