dipping glaze application weirdness

[Pir]

Hi, I'm new to glaze-making. While I'm just delving into making batches from scratch, I have a question about a commercial glaze that I purchased dry and added water to for dipping.

This is a Spectrum glaze called Autumn, and as you might see in the photos, it's... well, I'm not sure... collecting and dripping and drying unevenly.

The glaze measures a specific gravity of 156.  (Being a commercial glaze, I don't know the ingredients or their proportions.)

I mixed the glaze well before use. I ran a slightly damp cloth across the bisqueware (bisqued to 04) to remove dust and to prime the clay for glaze absorption.  I used dipping tongs for a 3-second in-and-out dip (longer for the tiny thin-walled bowl); after lifting out, I rotated the pot and gently shook of drips. The glaze seemed to dry quickly--and yet drips formed and ran, and then dried as visible drips.

I'll have to see how they fire. Test tiles came out great (on red clay bodies, not brown or buff), but the tiles were small and I didn't notice as much of this application ugliness.

Any ideas on what this problem is, or advice on how to fix it (if it's indeed a problem) are greatly appreciated! Thanks!

 

[liambesaw]

The fix depends.  It depends on what you want as the properties.

I personally would either wait a week and see if the glaze deflocculates itself (a lot of times this happens on its own).  Or deflocculate it myself with some darvan or sodium silicate.  This causes the glaze to dry faster by reducing the viscosity while keeping the water content the same.  

Another option is to flocculate, which would be adding a little epsom salts solution which will thicken the glaze and cause it to dry slower.  I don't like this because i hate waiting for glaze.

[Pir]

Thanks. I mixed the glaze some weeks ago; after a few days, it was still pretty mixed (nothing much settled). After a few weeks, there was settling (water on the top). I mixed it up last night, and this afternoon there was a small degree of separation and settling. So, it seems to be deflocculating (I think?). 

Another observation is that the dried glaze on the pot is quite soft and comes off easily on the fingers.

I could try two pint-size batches--one for deflocculating and one for flocculating... 

Thanks for your advice!

[Hulk]

I've gone wetter and jellier.

My post, copied from 

Uneven dipped glaze application - Clay and Glaze Chemistry - Ceramic Arts Daily Community

I'm having better dipping results after employing Tony Hansen's suggestions, here https://digitalfire.com/4sight/library/thixotropy_and_how_to_gel_a_ceramic_glaze_73.html

I'm thinning my glazes (I have some white and light blue premix powders, the rest are mixed from raw ingredients in my studio) to ~1.41 to 1.47 specific gravity (I'm keeping notes on each glaze), then adjusting thixotropy with Epsom salts ...then, much easier to apply glaze in even layer, not too thick, and they "gel" (that is, not run and drip!) better.

When piece is lifted out of the glaze bucket, a good grip helps, for a few sharp shakes helps to lose any drips, then wait for the glaze to mostly gel, and finally, smooth any drips with a wet finger before they set up, where the trick is to not smooth too soon, else the glaze will be thin there, and not too late, for the drip won't smooth. Viola! Hope that helps.

and from

White glaze problems - Studio Operations and Making Work - Ceramic Arts Daily Community

How "wet" the glaze is - ratio of water to solid matter - can be expressed in terms of specific gravity:

Specific gravity (digitalfire.com)

I'm running between 1.39 to 1.47 (per my notes - keep notes!!) for the several glazes I use, mostly mixed from raw materials (I don't plan to buy any more premix, but do plan to use the premix I do have until gone - a powder blue, bad clear, and a matte white). A wetter glaze allows a wider (longer) "window" of dip time to achieve desired thickness, but will take longer to dry. A wetter glaze may also be more prone to running/dripping, however, the undesirable movement can be ameliorated! A less wet glaze typically goes on too thickly.

How the glaze moves can be adjusted:

Thixotropy (digitalfire.com)

This is the hot tip! A wetter glaze that has been adequately "gelled" goes on like a dream! I'm not having to rush to avoid a too thick glaze layer; a shake or two takes care of drops at the rim; any remaining drops I'll just run around the rim; any other remaining drops, I'll wait several seconds for the glaze layer to loose its sheen, then smooth the drop with a wet finger*. Glazing (almost all dip/pour - very little brushing, no spraying) is much more fun for me now.

As I typically don't glaze fire twice a month (if that), I start out with thorough mixing, sieve, then check/adjust specific gravity, leaving thixotropy check for last. Turning the glaze with a large kitchen whisk (clockwise, easier on my hand, elbow, etc.) to the meter of "Positive Vibration" (Bob Marley's 1976 album), when stirring is ceased, I expect:

    the glaze to turn as a mass, with very little shear (iow, not much currents of differing speeds);

    the mass to continue turning for about three to four turns;

    the mass to slow and stop all together - again, very little currents of differing speed;

    the mass to "bounce back" a bit when it stops.

The desired behaviour - liquid when moving, gelled when not moving - is much more conducive to successful glazing than the "liquid until it dries" extreme (imo).

Inadequately gelled glaze will exhibit currents of differing speeds as it turns in the bucket (use round buckets; square buckets are bad, heh) - a portion of the glaze will just keep on spinning for quite some time, whilst shearing against the portion of glaze moving at a slower speed.

*Some prefer to allow droplets to fully dry, after which they can be levelled by "fettling."

[oldlady]

pir, a slightly damp cloth is not enough preparation for dipping.   depending on how many pots you are glazing, dipping the entire pot quickly, into a bucket of clean water works well.  letting the first few sit while you dip them all gives enough time for the bisque to even out the moisture content if you have several to do.   otherwise, the glaze will not go on evenly.

powdering should not happen, check the archives for that problem.

[Min]

4 hours ago, oldlady said:

a slightly damp cloth is not enough preparation for dipping

It can be, depends on the clay. I never dip pots in water before glazing, they are always dry when I glaze.

@Pir, I'ld rub those pinholes over with a dry fingertip when the glaze is dry.

[liambesaw]

1 minute ago, Min said:

It can be, depends on the clay. I never dip pots in water before glazing, they are always dry when I glaze.

@Pir, I'ld rub those pinholes over with a dry fingertip when the glaze is dry.

I also do not water my pots down.  I don't do anything to them before glazing except blow them off with an air hose to knock off any dust

[oldlady]

it is very hard to explain that i do not mean drown the pot and hold it underwater until it screams.   a quick dip will not get the pot wet, it will not even shine.  but the moisture will prevent the pot from greedily sucking up the wet glaze leaving an uneven surface.   and that quick dip takes less time than tediously wiping all surfaces.

usually there were more than 20 pots to glaze each time at my studio, they were dipped in water first and lined up before stirring and sieving the glaze.  by the time each pot was glazed, some time had gone by and they were never "wet".   

there are many words to describe moisture content, dry, damp, moist, wet, dripping.    it worked for me for many years until i started spraying glaze on greenware and single firing.  might work for someone else.

 

Edited February 8, 2021 by oldlady
correction for future readers

[Pir]

On 1/27/2021 at 8:11 AM, oldlady said:

pir, a slightly damp cloth is not enough preparation for dipping.   depending on how many pots you are glazing, dipping the entire pot quickly, into a bucket of clean water works well.  letting the first few sit while you dip them all gives enough time for the bisque to even out the moisture content if you have several to do.   otherwise, the glaze will not go on evenly.

powdering should not happen, check the archives for that problem.

Thanks! I'd never even heard of the damp cloth until watching Phil Berneburg vids (Washington Street Studio on YouTube).

[Pir]

On 1/26/2021 at 6:42 PM, Hulk said:

I've gone wetter and jellier.

My post, copied from 

Uneven dipped glaze application - Clay and Glaze Chemistry - Ceramic Arts Daily Community

I'm having better dipping results after employing Tony Hansen's suggestions, here https://digitalfire.com/4sight/library/thixotropy_and_how_to_gel_a_ceramic_glaze_73.html

I'm thinning my glazes (I have some white and light blue premix powders, the rest are mixed from raw ingredients in my studio) to ~1.41 to 1.47 specific gravity (I'm keeping notes on each glaze), then adjusting thixotropy with Epsom salts ...then, much easier to apply glaze in even layer, not too thick, and they "gel" (that is, not run and drip!) better.

When piece is lifted out of the glaze bucket, a good grip helps, for a few sharp shakes helps to lose any drips, then wait for the glaze to mostly gel, and finally, smooth any drips with a wet finger before they set up, where the trick is to not smooth too soon, else the glaze will be thin there, and not too late, for the drip won't smooth. Viola! Hope that helps.

 

Thanks Tom. I think I read your post earlier, or was otherwise already directed that Hansen video. I'm just not sure if the glaze in question needs deflocculating-- which is what I understand adding epsom salts or vinegar to be doing. It is sort of settling at bottom...but not hard-panning (if that's the word).

Am I understanding it correctly that before adding an acid, the glaze specific gravity should be lower (wetter/more water)?

One difficulty I have is that almost every time I measure SG--with a 100mL syringe, or in a 100mL beaker, or in a 50mL beaker and doubling--I get a different stinkin' number. Last week the glaze was 1.56, today it's 1.63 (has been covered all week); it remains 1.6-1.63 if I measure it in a 100mL beaker and 1.48-1.5 if in a 50mL and then double it. I know it shouldn't be but I've done it five times in a row. (I feel like I'm going crazy!)

I can say that stirring it, it takes about 5-6 seconds for the glaze "body" to come to a stop; there is no bounce-back. So, I'd assume that = thin?

How much acid does one add? I've seen "add a teaspoon at a time to a 5-gal bucket," but I was thinking of testing it out on 2 cups, first. I guess I'd add a drip or two?

Does the SG change after adding an acid? It should be thicker, but should will that make it heavier?

Thanks Much.

 

 

 

[Pir]

I brought about 75 ounces (2.25 liters) of the glaze to a 1.45 SG, then began adding an Epsom salt solution drip by drip while stirring... must've put 2 or 3 Tbs in there with little effect. Still takes about 7 seconds to come to rest after a stir, although there is a vague bounce-back, where at the end the glaze moves in the opposite direction a tiny bit.

Unsure if I should keep on a'drippin'...

[Babs]

Have a few test tiles or little pots and dip to see the effect.

SG not affected by defloc or floc.

[Callie Beller Diesel]

1 hour ago, Pir said:

One difficulty I have is that almost every time I measure SG--with a 100mL syringe, or in a 100mL beaker, or in a 50mL beaker and doubling--I get a different stinkin' number. Last week the glaze was 1.56, today it's 1.63 (has been covered all week); it remains 1.6-1.63 if I measure it in a 100mL beaker and 1.48-1.5 if in a 50mL and then double it. I know it shouldn't be but I've done it five times in a row. (I feel like I'm going crazy!)

You’re not going crazy. If you’re measuring in different containers, the different containers will give slightly different measurements due to calibration issues. Unless you’re getting really spendy lab containers (which aren’t necessary), some variation is considered acceptable.  If you keep using the same measuring device across the board, go by that device’s numbers to get repeatable and predictable results. 

 

1 hour ago, Pir said:

Does the SG change after adding an acid? It should be thicker, but should will that make it heavier?

It will be more viscous, but the SG number should stay the same. You’re affecting how the glaze flows (or rather doesn’t), not adding more dry material or water that would change that number. At least not enough liquid to be measured meaningfully, anyways.

 

1 hour ago, Pir said:

I'm just not sure if the glaze in question needs deflocculating-- which is what I understand adding epsom salts or vinegar to be doing. It is sort of settling at bottom...but not hard-panning (if that's the word).

If you’re adding Epsom or vinegar, you’re flocculating. If you’re adding Darvan or sodium silicate, you’re deflocculating. Flocculating will basically make the glaze more viscous in the bucket without changing the water level. It keeps particles suspended longer because they’re clustered together and allows for a fatter application that dries more slowly, which is one way of fixing your drip issue.  It also has the added benefit of preventing hardpanning. Even a flocculated glaze will settle out eventually, it just won’t turn into that hideous, cement-like substance we all know and hate. A flocculated glaze will just sort of gel at the bottom with a layer of water on top, and will stir up in a matter of a minute or two.

As much as I love Tony Hanson for everything else he does, Sue Macleod explains deflocculation and flocculation better than anyone else out there right now. Hers is an in-depth and user friendly explanation.

2 hours ago, Pir said:

Am I understanding it correctly that before adding an acid, the glaze specific gravity should be lower (wetter/more water)?

Only if that ratio of glaze materials to water is what will give you the application layer of your glaze that you want.  Making it too thin and then adding a flocculant can still make your glaze go on too thin.

[Min]

@Pir, I wouldn't add any more saturated epsom salts solution to that batch of glaze. Going forward I'ld suggest just scooping out 100mls or so of glaze and experiment with that by adding just a drop or two at a time then stirring it up and see if it's working with the glaze. Approx 1 teaspoon/ 5 ml per gallon should have done it. I made the mistake recently of using some epsom salts solution that had precipitated out enough to make it useless. Is your solution saturated? What cone is your bisque fired to? 

@oldlady, agree some clays need dipping in water, I've found it's mostly the open groggy bodies that this helps with to prevent air blowouts causing pinholes in the raw glaze.

[Hulk]

Hi Pir!

Agreed that checking sg is just for repeatability - do a thorough stir, getting all/any gel on the sides and bottom. The value would be significant if one were sharing results with others (who may use the different equipment, eh?), I suppose. Are  you able to get repeatable sg using same equipment? Watch the level, and any drips stuck on thar. I use a cheap plastic graduated cylinder, looking to get within a gram on repeated measurements o' same glaze...

I'm trying for same sg, very nearly same thixotropy as "last time," unless I didn't like how the glaze went on - if going on thick, lower sg; if running and dripping, more gel! Each glaze is a bit different, that's where the notes help somewhat...

I go wetter on account of it gives me more control of the thickness of the layer, and it also wets the nooks and crannies, any carving, etc much better - it covers better. I say more control because the same dip time as a "dryer" glaze yields a thinner layer; I don't have to be precise with the dip or pour time - the time window of success is bigger. Also, wetter on account of a "dryer" glaze that doesn't gel well - low thixotropy - will be unmanageable goop when jelled, won't it?

The Epsom salt or vinegar increases the thixotropy (gel); the glaze sheets off the ware, then stops moving. The glaze behaves as a liquid when moving; when not moving, it gels.

It  Just   Stops. That's the revelation in my glazing - the glaze doesn't just run and drip ...and drip and drip.

Staying suspended better is a side benefit for me - I want help with applying the glaze in an even well behaved layer. I don't mind that it takes a bit longer to fully dry.

Edited January 30, 2021 by Hulk
Jello

[Pir]

23 hours ago, Callie Beller Diesel said:

You’re not going crazy. If you’re measuring in different containers, the different containers will give slightly different measurements due to calibration issues. Unless you’re getting really spendy lab containers (which aren’t necessary), some variation is considered acceptable.  If you keep using the same measuring device across the board, go by that device’s numbers to get repeatable and predictable results. 

 

 

Thanks Callie. That makes me feel better! Although it doesn't quite compute... But it seems true--my 100mL beaker gave one result, the 50mL another, again and again.

[Pir]

On 1/29/2021 at 6:02 PM, Callie Beller Diesel said:

If you’re adding Epsom or vinegar, you’re flocculating. If you’re adding Darvan or sodium silicate, you’re deflocculating. Flocculating will basically make the glaze more viscous in the bucket without changing the water level. It keeps particles suspended longer because they’re clustered together and allows for a fatter application that dries more slowly, which is one way of fixing your drip issue.  It also has the added benefit of preventing hardpanning. Even a flocculated glaze will settle out eventually, it just won’t turn into that hideous, cement-like substance we all know and hate. A flocculated glaze will just sort of gel at the bottom with a layer of water on top, and will stir up in a matter of a minute or two.

As much as I love Tony Hanson for everything else he does, Sue Macleod explains deflocculation and flocculation better than anyone else out there right now. Hers is an in-depth and user friendly explanation.

 

Oh, right! And I think the glaze was flocculated--or in a "floccululent condition"--already, because it was gelled at the bottom, water at the top, and easy to mix quickly. 

(I guess I'm back to not understanding the weirdness of the glaze--how it drips but then dries so quickly the drips remain. And how soft the dry glaze is on the body. If I dip with no movement, the application is more or less even.)

I'll check out Macleod--I had just subscribed to something or other of hers.

[Pir]

22 hours ago, Min said:

@Pir, I wouldn't add any more saturated epsom salts solution to that batch of glaze. Going forward I'ld suggest just scooping out 100mls or so of glaze and experiment with that by adding just a drop or two at a time then stirring it up and see if it's working with the glaze. Approx 1 teaspoon/ 5 ml per gallon should have done it. I made the mistake recently of using some epsom salts solution that had precipitated out enough to make it useless. Is your solution saturated? What cone is your bisque fired to? 

@oldlady, agree some clays need dipping in water, I've found it's mostly the open groggy bodies that this helps with to prevent air blowouts causing pinholes in the raw glaze.

Thanks, Min. I did start small, but I was doing the stir test, and a bigger bucket/amount seemed better... I'll have to see if I've ruined that portion now. Thanks for the quantity info!

I think it was a saturated solution, I found a "30g ep salt dissolved in 100ml of water" formula, but adding more, it still dissolved.

I wonder now if the salt had no effect because it wasn't saturated. I'd think it should've made some difference...?

I fire bisqueware to 04. That's mainly because my friend does, and I use his little shed-studio. I considered 06, but there are so many other variables I'm contending with--I'm still playing with different sorts of clays, and now just beginning to follow glaze recipes in search of a good base clear glaze. What I'm finding with this clear glaze might be some general truisms... 1.) On some mid-range clays (speckled buff) it doesn't craze, and appears transparent (although under a magnifying glass I see a zillion tiny bubbles); on other bodies (Calico red) it crazes like crazy, and on some a bit (brown); 2.) the SG is 1.45, but with higher specific gravity it crazes more; and with lower specific gravity, it also seems to craze more; 3.) heavier applications seem to produce more crazing, on those bodies that craze.

The clear recipe has a lot of neph sy and some Gerstley borate, and the K and Na content I understand can cause crazing. I'm thinking about tinkering with the proportions or trying a new recipe.

Well, I guess I'm thinking out loud now. I never thought two years ago that as I was learning how to throw there'd be SO MUCH MORE to learn. It's a good thing, though.

Thanks again, Pir

[Min]

1 hour ago, Pir said:

I think it was a saturated solution, I found a "30g ep salt dissolved in 100ml of water" formula, but adding more, it still dissolved.

 

If you start with hot water you could probably get more than that in there, keep adding it until no more will dissolve. As the water cools the epsom salts solution will hold what it can and the excess will precipitate out.

Since we don't know what's in your commercial glaze there is the possibility it is low in clay (kaolin or ball clay), glazes low in clay don't respond well to flocculants so adding 2% bentonite to glazes with less than 10% clay gives the flocculant something to work with. Clay in the glaze also helps toughen up the raw glaze so it's less prone to being dusty and soft when dry. Since you did mention the raw glaze is dusty it might be worth adding a small amount of bentonite to a test amount of of glaze. If you try this the bentonite won't mix with a wet glaze well. You would have to weigh out the bentonite then mix it with a small amount of hot water then blend that into the glaze. See if the epsom salts solution works better with the bentonite added test sample.

With some glazes the drips in the raw glaze don't really matter/show in the fired glaze, others not so much. Have any test pots you can fire and see if the drips really are a big deal or not?

^04 for bisque is good, I'ld stick with that. I asked just in case you were bisque firing really low in which case it could account for the pinholes in the raw glaze on your pots.

 

1 hour ago, Pir said:

the SG is 1.45, but with higher specific gravity it crazes more; and with lower specific gravity, it also seems to craze more; 3.) heavier applications seem to produce more crazing, on those bodies that craze.

Glaze being thinner is just a band aide solution for crazing, it will still craze over time if the heavier application crazes.

1 hour ago, Pir said:

I never thought two years ago that as I was learning how to throw there'd be SO MUCH MORE to learn. It's a good thing, though.

Yes! There is always something to learn in this field!

[Pir]

22 hours ago, Min said:

Since we don't know what's in your commercial glaze there is the possibility it is low in clay (kaolin or ball clay), glazes low in clay don't respond well to flocculants so adding 2% bentonite to glazes with less than 10% clay gives the flocculant something to work with. Clay in the glaze also helps toughen up the raw glaze so it's less prone to being dusty and soft when dry. Since you did mention the raw glaze is dusty it might be worth adding a small amount of bentonite to a test amount of of glaze. If you try this the bentonite won't mix with a wet glaze well. You would have to weigh out the bentonite then mix it with a small amount of hot water then blend that into the glaze. See if the epsom salts solution works better with the bentonite added test sample.

With some glazes the drips in the raw glaze don't really matter/show in the fired glaze, others not so much. Have any test pots you can fire and see if the drips really are a big deal or not?

That (bentonite) sounds like an idea!

Here is "Autumn" (Spectrum), all "Caclio  Red" clay. Drips are great! On the bowl they seem like drips. The bowl was moved around in the glaze more than the others, I suppose, if that has anything to do with it. The two on the right were dipped in more even-handedly, and exhibit beautiful bands. The cup on the left was a brush-on version. It was by far the best example--the glaze utterly doesn't work on my other clays (no blues, all dark amber), and even these dipped pieces don't match the quantity and quality of that blue (pic a bit dark).

I think may I need a longer dip...

Thanks again for your input.

[Chilly]

On 1/30/2021 at 2:02 AM, Callie Beller Diesel said:

Sue Macleod explains deflocculation

A quick google found this:

https://suemcleodceramics.com/how-to-make-a-saturated-epsom-salt-solution-to-flocculate-your-glazes/

 

[Pir]

Thanks again to Hulk, Min, Callie and others for answering questions I had in 2021... which are similar to the ones I've posted (and you've answered) this year! It's taken so long for some of these concepts to sink in.

Pir

[Kelly in AK]

Because this thread woke up, I read it and was delighted to see a “problem solved” outcome. Happy times.

For others in the future, I want to say @Hulk‘s first response explains a comprehensive and reliable solution to application frustration.

 I’ve never bothered with specific gravity, I’m too lazy, but I generally follow the principles he lays out. My glazes go on smoothly, at the right thickness, and don’t hardpan in the bucket. 

My fast and loose version is this: 

Mix the glaze and sieve it twice. Get enough water in it until it looks right when you dip your dry fingers in it (That’s experience and I believe measuring s.g. will allow you to bypass this “gut feeling” method.). It ought to coat your fingers thinly, not thick or goopy and not running off all watery. It’ll be way too runny and thin to apply at that point. Lots of drips and dries too fast*. Add saturated Epsom salts solution a little at a time until the viscosity is right- stir vigorously, pull out the mixing tool and count seconds. It should stop spinning by four or five seconds. If you over flocculate, add water a little at a time until viscosity is good.

Most of my glazes use frits, not Gerstley borate, which is a unique glaze gelling animal. Less flocculant required for those with much G.b.

*When I say “dries too fast,” I mean the runs and drips where you poured or dipped will have frozen in place before you even finish dipping, pouring, or brushing. I don’t have to wait around for my glaze to dry, but I also don’t have to rush the job to avoid a sloppy looking application. 

[Pir]

5 hours ago, Kelly in AK said:

Mix the glaze and sieve it twice. Get enough water in it until it looks right when you dip your dry fingers in it (That’s experience and I believe measuring s.g. will allow you to bypass this “gut feeling” method.). It ought to coat your fingers thinly, not thick or goopy and not running off all watery. It’ll be way too runny and thin to apply at that point. Lots of drips and dries too fast*. Add saturated Epsom salts solution a little at a time until the viscosity is right- stir vigorously, pull out the mixing tool and count seconds. It should stop spinning by four or five seconds. If you over flocculate, add water a little at a time until viscosity is good.

Most of my glazes use frits, not Gerstley borate, which is a unique glaze gelling animal. Less flocculant required for those with much G.b.

*When I say “dries too fast,” I mean the runs and drips where you poured or dipped will have frozen in place before you even finish dipping, pouring, or brushing. I don’t have to wait around for my glaze to dry, but I also don’t have to rush the job to avoid a sloppy looking application. 

Hi Kelly, I'm obsessed with SG, but I never sieve twice! I'm hoping that sieving twice isn't that important--but please correct me if I'm wrong.

I'm just getting around to attempting to substitute Gerstley Borate with a frit, but I'm finding I will need to some extra Glazy experience/training (I've done simple substitutions, like MgO for talc, but I was stumped when trying to sub a frit).

I was comparing two floating blue recipes, one with GB, and a Britt version with a frit, and his recipe reflected perfectly what Hansen writes about regarding the benefits of such a sub: the frit drastically lowers the GB (the frit supplies boron, but doesn't gel the glaze like GB); he adds more EPK to suspend and to supply Al (frit had no Al); he uses less neph sye (frit had sodium).

I've used epsom salts before, successfully, but last night I tried it in a simple white mat recipe (which applies just awfully)-- neph sye 35 / dolomite 20 / whiting 5 / EPK 20 / silica 20 --but the epsom salts did NOTHING! I brought the glaze down to 1.44 or 1.45. I used a concentrated solution; I made another batch to be sure it was super concentrated; I added a liquid bentonite (my suspicion was that more clay might be needed?); and then I even added vinegar (last ditch efforts), and nothing got that damn glaze any better--i.e., it remained thin on the finger; it dripped all over the test tiles; it kept spinning in the bucket; it never bounced back, reflecting thixotropy.

I'm going to post this on my other thread to see if anyone has any ideas...  Low specific gravity but THICK! 

Pir

 

Edited November 15, 2022 by Pir

[Bill Kielb]

3 hours ago, Pir said:

neph sye 35 / dolomite 20 / whiting 5 / EPK 20 / silica 20 --but the epsom salts did NOTHING! I brought the glaze down to 1.44 or 1.45. I used a concentrated solution; I made another batch to be sure it was super concentrated; I added a liquid bentonite (my suspicion was that more clay might be needed?);

Generally recipes with 10% clay or more won't need bentonite. Your recipe has 20% EPK already which many find a bit high.