The issue with Laguna Iron Phoenix glaze...

[Rex Johnson]

Not sure anyone here uses this commercial glaze but I've had some good varying results.

Laguna MS‑128 Iron Phoenix Glaze

I've used it on varying pots for the past three years but this year was different. On cone 6 clay the first year in was marvey,

Second year it became sort of unstable, crawling and flaking.

I use 3 gallon buckets. The buckets sit outside and covered year-round. This year I mixed a fresh 5-10 lbs I'd normally use.

But the application when dipped over say a Pete's gloss black, turned to flakes. It flaked off essentially.

Sprayed onto pots by itself it crawled and didn't gloss up like in the past.

Granted, I went from cone 6 clay to cone 10 clay. But it's odd that there seems to be a breakdown on what seemed to be a stable glaze has now turned uncertain...

Laguna instructions say: " For best results add water and mix Satin Texture Glazes right before use. Due to the chemical composition of these glazes, they are best used right after they are mixed with water. When left sitting overnight after the water has been added, it is our experience they will 'jell up'. If water is added after 24 hours to correct the thickness, the glaze tends to crawl. "...

This seems odd to me.  Is Laguna saying you need to use up all the glaze in one sitting???

Weird.  I used this glaze all thru the season off and on the first year without any problems.

First year use (outside of the bowls shown)  VVV 

[Pres]

I would ask a few questions here. When did you change clay bodies, why? Have you sieved this glaze since mixing it, second year, third year? What is your current cone temp for your firings?

 

best,

Pres

[Mark C.]

The issue with commercial glazes is you do not know whats in them or how to fix them.

I can add that your body cone 6 to then 10 is a big issue but you already know this.

The only other point is Laguna makes glazes with the cheapest materials they have in glazes -meaning silica (most likely 200 mesh) etc etc.

I know this as they make glaze for me in 1 ton lots, but I specify the materials vs let them use the cheapest which they did the 1st batch.

On the plus side they usually are the cheapest suppler around.

One last factoid they have a New owner as John Brooks sold it this year.

[Rae Reich]

I think they're saying "mix up only what you'll use in one day". That's a new one to me!

You're not single firing, are you? 

[Min]

If you look at the MSDS for that glaze it lists 3% (maximum) of lithium carbonate. Lithium carb is slightly soluble in water plus it can form crystals in the glaze slurry. If you leave the glaze sit for extended periods and get these glaze slurry chunks and then toss them when re-sieving or don’t melt them down and add back to the bucket you are going to alter the glaze. The MSDS also shows zinc (or zinc compounds) at 23% (max). If it is zinc oxide that seems like a heck of a lot for a non macro crystalline glaze.

re:When left sitting overnight after the water has been added, it is our experience they will 'jell up'. If water is added after 24 hours to correct the thickness, the glaze tends to crawl. “...

I would measure the specific gravity of the glaze when just mixed and when it’s working how it’s supposed to then go by that when using this glaze, not by how it looks when it gels up. 

re crawling over your gloss black, that might be an application timing issue. If the base glaze is dry then when you put the second glaze on top of it then the water in the top glaze will rehydrate the base and cause it to lift. Have you tried putting the top layer of glaze on as soon as you can handle the pots? Not all glazes are incompatible like this but since it's a commercial glaze we don't really know what's in it so can't change clay content etc

Have all firings been done in oxidation? Any chance the pots that "didn't gloss up" were fired in reduction?

+1 for what Mark said about using a ^10 clay at ^6

[Rex Johnson]

Yes I admit many variables here, any probably no easy answers. Just rolling the dice hoping someone her might have similar issues.

I mixed the new batch into the old batch (that worked well).

I sieved all my glazes at least three times before the glazing began about 2 weeks ago.

The last firings have been a mix of light reduction at some point during the firing. Nothing  to see here.

Yeah the flaked up sauce over the other would have been done not within less than 10 minutes after the first application.

I have seen this glaze buckle up and flake off leaving bare areas. That started though last year on some very large pieces. I figured it was my sloppy application or other.

One thing I noticed is right after this glaze is mixed or re-mixed, it bubbles up in the bucket, like it retains air and makes little bubbles.

Weird science.

[Min]

Still gotta go back to thinking the 23% zinc or zinc compounds as listed in the MSDS is contributing to the glaze crawling. Also, it's my understanding that zinc in reduction firings is useful at the lower end but goes up the chimney for the most part, don't think this glaze was made for reduction firings. If there is spodumene in the glaze it can quite often have soap residue on it, it literally can make bubbles in the glaze slurry. 

[glazenerd]

I recall getting an email forwarded from Laguna, by my supplier. They were looking for crystalline  glazers to test several new zinc varieties. Their existing supplier ( Horsehead Cerox 506) had discontinued production, and they were testing four new zinc products. One from China, and three from Zinc Nationale (Mexico) as I recall? They had been using a white French process zinc that was giving them some issues.

White zinc is French process that will begin vaporizing at 2260F +/- (tested). Yellow zinc is sphalerite (American process), which can fire up cone 11 without issue.(tested) You may very well have gotten a batch during this period of transition?  The ingredients in the MSD sheet only add up to 70% or so, which means 30% of something is not listed. Most likely Nep Sy, which has 14-20% soluble salts pending mineral source.  Sodium will certainly form crystals as it sits, which if discarded during sieving would alter the flux level in the glaze. If enough sodium, along with lithium crystals were sieved out: it would effect the melt and clay/ glaze interface.

[Guest JBaymore]

1 hour ago, glazenerd said:

The ingredients in the MSD sheet only add up to 70% or so, which means 30% of something is not listed.

Don't ya' just love his stuff.  We have no idea what maybe about 30% of the material in there IS.  Firing issues aside........ what might be any health considerations about that 'missing matter'? The actual "policing" of MDSDs is not all that stringent. 

best,

...........................john

PS:  hum....... missing matter.  Maybe it is "Dark Matter".

[Magnolia Mud Research]

2 hours ago, JBaymore said:

..... hum....... missing matter.  Maybe it is "Dark Matter".

or maybe it just don't matter.   

LT

[glazenerd]

Glaze chemistry begins to matter when your glaze starts peeling off your pot.

What you breath in does matter: in 1978, I worked on a rehab job in South St. Louis city. Every day, we would use a compressor to blow off all the dust that accumulated on us from working. After a month, a city inspector shut down the job once they figured out that dust was asbestos . All the overhead pipes had 4" pure asbestos pipe insulation. Back in the days before asbestos became a big concern, and masks were an after thought.