Crawling Glazes

[Stillwater]

We have 27 glazes in our studio. Some crawl at times. Usually cracking appears on the dried glazed piece as though the glaze is having an adhesion problem.

 

Glazes often get very thick a day or two after mixing and need more water added. I use distilled in mixing and to thin.

 

I'm thinking an additive may help adhesion. Any thoughts?

[Callie Beller Diesel]

Wet the pot before glazing. Rinse it off quick in a bucket and let it dry for 15 minutes, and then dip. Try that before adding anything more complicated to glaze buckets used by a large group.

[High Bridge Pottery]

Too much clay, you can try and calcine half.

[oldlady]

after trying the dampening bisque, try watching youtube, john britt flocculating and deflocculating glazes.  i just watched it again and slowed it down several places because he assumes a lot of knowledge i do not necessarily have at my fingertips.  pay attention to the two test tiles that are covered with a red looking glaze that is cracking off.

[Babs]

Well I am loking for a crawling glaze, had one years ago that crawled and gooped beautifully, lost the recipe.

Anyone help wit that?

[Min]

@ Stillwater, like you said most glazes thicken up the next day as the clay etc in the glaze absorbs water then swells up. I wouldn’t add any gums etc to fix but work on getting the correct specific gravity for each glaze. If the bisqued pots are all fired to the same cone then dipped for about  the same amount of time in a glaze that isn’t too thick you shouldn’t get crawling (if the glaze thickness is the culprit). Really only takes a few minutes to check s.g. Glazes can be rechecked before use until your studio members get to know what they should look like when at a good s.g.

 

Like HighBridge said any glaze with more than 25% clay content would likely benefit from having 1/2 of it calcined. Then work out the LOI for the calcined clay and make allowances for the weight differences in your recipes. You don’t mention if it’s always the same glazes but it didn’t sound like it so not sure this is the problem. 

 

Layering 2 different glazes can cause crawling too but you would see this as they dry.

 

Also wondering if some of the pots with crawling had been sitting around and getting dusty and not wiped down before glazing? 

 

@Babs, try adding between 10 - ? magnesium carb to any glaze, you will get crawling. (you don’t even have to fire the test pieces to see how much to add for the initial tests. If you don’t see cracks in the glaze when it dries there isn’t enough, if the glazes cracks but pulls all the way off the pot then there is too much) Not sure if you are firing earthenware or midrange so not sure on the max amount of magnesium carb.

[Marcia Selsor]

if you have Gerstley Borate in the mix, that will thicken overnight. Add more water. Bentonite can expand, but I think it is Gerstley Borate.

Marcia

[Marcia Selsor]

Well I am loking for a crawling glaze, had one years ago that crawled and gooped beautifully, lost the recipe.

Anyone help wit that?

Start with adding 10 % Magnesium Carb. and increase in increments of 5%until you get what you want.

Marcia

[Babs]

ThanksMin and Marcia.

C6 but I'll get on with it.

[High Bridge Pottery]

Am I getting deja vu Babs or have you been searching for this recipe for a long time? Sure I remember this MgCO3 chat a few times. Do you have a picture of said glaze?

[Babs]

High Bridge, I had a glaze that crawled on my new body, and was trying to resolve that issue.

No I am trying to make a few platters, theme "time and tide," and was thinking along the lines of the crawled goopy glaze effect on the rims and across part of hte platter to suggest the mudflats of estuaries but couldn't find my recipe for the crawly goopy glaze.

SO I will do as Min and MArcia suggest and maybe come up with something.

My old glaze was white and it gooped beautifully over earthenware. Pre the present photograph everything era.

[PeterH]

Marcia: Start with adding 10 % Magnesium Carb. and increase in increments of 5%until you get what you want.

 

A picture to go with that.

https://digitalfire.com/4sight/images/materials/tigxitipup.jpg

...from https://digitalfire.com/4sight/glossary/glossary_crawling.html

[Min]

ThanksMin and Marcia.

C6 but I'll get on with it.

 

For ^6 you will likely need about 30% + magnesium carb. The old Beady Eyes Recipe would be a good start. I found it really lived up to it's name, if it's too melty I would just add a bit more clay and / or decrease the frit. I've used it with 10 zircopax to make it a clean crisp white,

Beady Eyes ^6

Custer 25

Whiting 6

Magnesium Carb 35

Ball Clay (I used OM4) 10

Silica 8

3134 16 (can you get 3134 in Oz?) can't remember if you use that or 3124?

100

 

plus 10 zirco

 

this is another one, lots of ingredients, I came up with it when messing around combining recipes, it's more goopy than cracked earth looking.

 

crawl feb 2009

Code Number:

 

Minspar  15.90 

3134 20.20

Talc 5.30

EPK 10.60

Magnesium Carb 31.90

Zircopax 10.00

Nepheline Syenite 13.30

Calcium Carbonate 3.20

Ball Clay 5.30

Silica 4.20

119.90

[Babs]

Thanks Min my original one actually beaded up thought it could be pebbles on a forshore sorta.

Will try your recipes. Thanks so much.

[Babs]

Thanks Peter White glaze in photo getting there

May go to lower firing as terracotta is ok for this project

[Babs]

Min this is your chicklet glaze with a light touch of vanadium wash over it.

Blue glaze also has a touch of vanadium wash across a section of it.

Platter hand formed. ^6 electric.

[Min]

Moonlit mudflats.jpg

Min this is your chicklet glaze with a light touch of vanadium wash over it.

Blue glaze also has a touch of vanadium wash across a section of it.

Platter hand formed. ^6 electric.Moonlit mudflats.jpg

 

Are you happy with how it turned out? (for some reason my computer is being fussy and I can't enlarge the photo to really see the crawl)

[Babs]

Well I'm having that prob. Too..

I'm ok with it, turned out quit matte which fitted the idea I had.

Feel ut would have handled fired a bit higher.

Will play with reposting image, but prob my photo,taken on phone isn't good enough.

Thanks Mib.

[Stillwater]

Thank you for your responses.  Wondering what your thoughts are on the following additives. Borax and Bentonite

The major crawling offender is the Dessert stone glaze base posted below. We use several base recipes. This is just one.

The glazes that crawl are taking a long time to dry.

When using more than one dipped layer cracking and peeling off in the drying stage is greatly increased.

 

 

Since I first posted we have tested an addition of bentonite 4%. to the inky black glaze

This seemed to help with adhesion and significantly reduce cracking

 

In a separate test, We added 5% Borax. to the dessert stone base....This did two things

1.  it immediately thinned out this glaze

2. Cracking was significantly minimized.

 

The addition of Borax did change the fired color and appearance of this glaze a bit.

 

I'm guessing that in the Dessert Stone AGB base there may be a flocculating issue causing us to add too much water to thin the glaze. When testing specific gravity the numbers actually go up when adding water!

 

Desert Stone (AGB)

Code #

M5

Materials Amt Nepheline Syenite 44.000 43.14% Whiting 16.000 15.69% Flint 15.000 14.71% EPK 8.000 7.84% Talc 11.000 10.78% Zinc Oxide 3.000 2.94% Titanium Dioxide 3.000 2.94% Additions Amt Cobalt 2.000 1.96%

Total:102.00

Unity Formula

CaO 0.43 MgO 0.23 K₂O 0.06 Na₂O 0.18 (KNaO) 0.24 ZnO 0.10 TiO₂ 0.10 Al₂O₃ 0.34 SiO₂ 2.28

 

Si:Al Ratio

6.7:1

Calculated

Expansion

7.9

LOI

9.0

Cost

1.40 per kg

 

 

 

Inky Black

Code #

G10

Materials Amt Soda Feldspar 15.000 14.29% Ferro Frit 3134 25.000 23.81% EPK 25.000 23.81% Silica 25.000 23.81% Wollastonite 10.000 9.52% Additions Amt #6650 Mason Stain 5.000 4.76%

Total:105.00

Unity Formula

CaO 0.73 K₂O 0.03 Na₂O 0.23 (KNaO) 0.26 B₂O₃ 0.34 Al₂O₃ 0.51 SiO₂ 4.34

 

Si:Al Ratio

8.5:1

SiB:Al Ratio

9.2:1

Calculated

Expansion

6.5

LOI

3.7

Cost

2.36 per kg

 

[Babs]

Sorry to high jack your post

I posted earlier with a similar prob.

Glazes cracking and peeling off pots

http://community.ceramicartsdaily.org/topic/13117-glaze-cracking-and-dropping-off-pot-before-firing/?hl=%2Bglazes+%2Bpeeling+%2Bfrom+%2Bpot&do=findComment&comment=96147

1st glaze If your glaze thickens after a day say, maybe a drop of sodium silicate will thin it without adding the extra water..which can cause trouble.. I'm not remembering too well, but this did help a bit with mine

2nd glaze calcine half the clay.

Not  a scientist here but just saying from doing.

[Pieter Mostert]

I think the Desert Stone AGB is being flocculated by the high Neph Sy content. From the digitalfire entry on Nepheline Syenite:

 

However, the place where you may note the solubility of nepheline the most is in glaze slurries containing significant percentages, they can gel over time and the addition of more water to thin the slurry can wreak havoc with application performance (try adding a few drops of deflocculant instead).

 

It's really weird that the specific gravity goes up when you add water. Do you have the numbers?

 

In my (limited) experience, glazes with borax tend to be thicker, so it's strange that adding borax thins your glazes. Hopefully someone who understands flocculating / deflocculating better than I do can explain this.