Powdery Application of Dry Mix Dip Glaze

[VeronicaP]

I purchased a dry mix white glaze from Laguna Clay. A few things: during mixing I added water, then the 25bag of dry glaze, then mixed with a drill and left over night (with a total of 2.5 gallons of water). 
 

fast forward a week and I tried dipping my pieces into the glaze and was so disappointed to find that the mixture dried very powdery/chalky so I’m thinking it’s not a good application and may cause crazing. I did go back and sieve after the fact but it only helped some.
 

It’s the first time I’ve tried mixing my own dipping glaze or using Laguna Clay mix. Should I add gum? What will I risk by firing the few pieces I’ve already glazed?
Thank you for any help. 
 

[Min]

Hi Veronica and welcome to the forum.

A powdery glaze application generally means there is little clay in the glaze recipe. Given that this is a commercial glaze we can't accurately alter the recipe to include some clay. To fix a powdery glaze adding some CMC gum solution will harden up the raw glaze layer but it will make the glaze take longer to dry. Since the glaze is already mixed with water you will have to mix up a CMC and water solution then add some of that to the wet glaze and if necessary allow the glaze to evaporate some of the excess water off. Are you measuring specific gravity or just going by 25 lbs of dry glaze to 2.5 gallons of water? Does the glaze settle to a hard layer at the bottom of the bucket?

Crazing won't be determined by a powdery glaze application. Crazing is due to a mismatch of glaze fit to claybody, glaze is too small for the clay it's on and therefore crazes.

[Callie Beller Diesel]

Application can effect how the glaze looks after it’s fired, but that has more to do with its thickness than if it’s powdery or not. You mention that you stirred the glaze more thoroughly for a second application: how well you stir the glaze can also affect how well it goes on. Some glaze ingredients have larger particle sizes and will settle out faster than others. If those particles are still mostly at the bottom of the bucket when you dip, you’re leaving out important glaze ingredients. Odds are good your application might be a bit weird, from what you’ve described. You have 2 choices, and it depends on how precious the pieces are to you. You can fire them and get information on what happens (my first choice). or you can rinse the glaze off and try again after your bisque has dried completely. 

 

If you need a quick and dirty trick for getting a powdery glaze to stay in place a bit better, you can spray any already glazed pieces with hairspray or laundry starch. It’s not ideal to use for large batches, I’m just thinking it’d help if you have to handle the pieces you’ve already glazed a bit. 

 

[VeronicaP]

10 hours ago, Min said:

Hi Veronica and welcome to the forum.

A powdery glaze application generally means there is little clay in the glaze recipe. Given that this is a commercial glaze we can't accurately alter the recipe to include some clay. To fix a powdery glaze adding some CMC gum solution will harden up the raw glaze layer but it will make the glaze take longer to dry. Since the glaze is already mixed with water you will have to mix up a CMC and water solution then add some of that to the wet glaze and if necessary allow the glaze to evaporate some of the excess water off. Are you measuring specific gravity or just going by 25 lbs of dry glaze to 2.5 gallons of water? Does the glaze settle to a hard layer at the bottom of the bucket?

Crazing won't be determined by a powdery glaze application. Crazing is due to a mismatch of glaze fit to claybody, glaze is too small for the clay it's on and therefore crazes.

Thank you Min, this is extremely helpful. I haven’t tested the gravity but it’s consistency is slightly thicker than skim milk. Its not a hard layer exactly, but more like mud. 

[VeronicaP]

8 hours ago, Callie Beller Diesel said:

Application can effect how the glaze looks after it’s fired, but that has more to do with its thickness than if it’s powdery or not. You mention that you stirred the glaze more thoroughly for a second application: how well you stir the glaze can also affect how well it goes on. Some glaze ingredients have larger particle sizes and will settle out faster than others. If those particles are still mostly at the bottom of the bucket when you dip, you’re leaving out important glaze ingredients. Odds are good your application might be a bit weird, from what you’ve described. You have 2 choices, and it depends on how precious the pieces are to you. You can fire them and get information on what happens (my first choice). or you can rinse the glaze off and try again after your bisque has dried completely. 

 

If you need a quick and dirty trick for getting a powdery glaze to stay in place a bit better, you can spray any already glazed pieces with hairspray or laundry starch. It’s not ideal to use for large batches, I’m just thinking it’d help if you have to handle the pieces you’ve already glazed a bit. 

 

Thank you so much Callie, very helpful info. I’m going to try a finer sieve to strain with. I’ll test one of the pots and hold the others to the side until I can see the results and go from there.

[Callie Beller Diesel]

The mesh of your sieve won’t make it more or less powdery: that’s just how some materials dry. If you’ve already used an 80 mesh, it’s sieved plenty. 

Usually you only have to sieve it when you first make the glaze, when you add more material to the batch, if it’s been sitting a long time and has stubborn lumps, or if there’s been a LOT of stuff collecting on the side of the bucket and it gets scraped back in. If you wipe the bucket down at the end of a glaze session and use it every 2-3 weeks, mostly you only have to mix it thoroughly for a few minutes before using.

[neilestrick]

Most commercial glazes are primarily sold as wet mix, which has the necessary additives to harden the surface. When they sell them as a dry mix they don't have those additives, and they don't necessarily formulate them to dip well in the first place. If it is very powdery, then it probably doesn't stay suspended very well either, so I would start by adding 2% bentonite (by dry weight) to your mix. Bentonite tends to clump into sticky globs when you mix it with water, so it's best to dry mix it with your other ingredients first. Since you've already mixed your glaze, try taking an equal amount of your dry glaze (if you have any left) and mixing it with the needed amount of bentonite for the whole batch, and use a hand blender to get it smooth before adding to the big batch. If you've used all of your dry mix, just mix bentonite, some water, and some of the wet glaze and blend it well to get the globs out. That may harden it enough that it's not a big issue.

CMC gum will also harden the surface, but it will affect the water content of the glaze slurry, and it tends to decrease in effectiveness as it ages and bacteria eats it up. Adding about 1/4% copper carbonate to the mix will help to preserve it, and shouldn't affect the glaze color, although I would test it first.

I mix my glazes to a chocolate milk consistency, not skim milk. Not being silly here, think of a good thick chocolate milk that coats the inside of your mouth. At that consistency a 6 count dip is perfect.

[PeterH]

36 minutes ago, neilestrick said:

If you've used all of your dry mix, just mix bentonite, some water, and some of the wet glaze and blend it well to get the globs out

I found this an interesting suggestion on how to add bentonite to a wet glaze. It's based on slaking the bentonite before any agitation/mixing.

How to Add Bentonite to a Wet Glaze
https://suemcleodceramics.com/how-to-add-bentonite-to-a-wet-glaze/

The sprinkle-on-water, slake, stand, remove-excess-water method looks like a low-risk way to try out the idea; revert to plan-A if it's lumpy.

[Callie Beller Diesel]

Caveat to anyone who might be reading this thread in the future: check with the manufacturer before you start adding stuff to your pre-purchased dry glaze. I think there are some places that might include bentonite in their recipes, which can play havoc with any additives. Check the supplier’s website for any mixing instructions first, and reach out to them to see if they have any recommendations before you start amending your glaze slurry with gum, bentonite, Epsom salts, vinegar or Darvan. You won’t be the first person to have these questions: someone will help you. If you don’t want to wait for someone’s email reply, don’t test a substance on your entire bucket: remove a sample and see what your chosen additive does first. 

Laguna has these mixing instructions on their website, and nothing in them contraindicates adding either gum or bentonite. They do mention using a hydrometer to measure SG, but most of those who speak up on this forum prefer using a 50 or 100ml syringe to weigh it, as that’s more accurate for our purposes. But that last is me being picky.