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I'm looking for some advice on testing pottery for dishwasher safe cleaning. I used the test Mastering Cone 6 Glazes recommends (5% soda ash solution and simmer for 6 hours) and I don't think my results are accurate. Maybe I did more of a boil than a simmer?

Anyways, everything that came out of the test basically lost a good amount of gloss. Why I say I don't think my results are accurate is because the exposed clay portion turned pretty white as well. I have been washing a set of pottery dishes in my dishwasher for about the past 5 years and the exposed clay portion on the bottom of that ware is no where close to what my results look like with the Mastering Cones 6 Glazes test. Also, I tested some recipes they provided in their book and did a whole lot of work with glaze calculation software to get the percent makeup of materials as close to their Unity formula and they said they considered these glazes durable. So, I find it hard to believe what I did was correct, seeing everything else I've followed from that book has been spot on with getting the same results.  

I'm trying to figure out if I did something wrong or if the test isn't that accurate. What advice you you have? 

Thanks,

Dan

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2 hours ago, DBPottery said:

I'm looking for some advice on testing pottery for dishwasher safe cleaning. I used the test Mastering Cone 6 Glazes recommends (5% soda ash solution and simmer for 6 hours) and I don't think my results are accurate. Maybe I did more of a boil than a simmer?

Anyways, everything that came out of the test basically lost a good amount of gloss. Why I say I don't think my results are accurate is because the exposed clay portion turned pretty white as well. I have been washing a set of pottery dishes in my dishwasher for about the past 5 years and the exposed clay portion on the bottom of that ware is no where close to what my results look like with the Mastering Cones 6 Glazes test. Also, I tested some recipes they provided in their book and did a whole lot of work with glaze calculation software to get the percent makeup of materials as close to their Unity formula and they said they considered these glazes durable. So, I find it hard to believe what I did was correct, seeing everything else I've followed from that book has been spot on with getting the same results.  

I'm trying to figure out if I did something wrong or if the test isn't that accurate. What advice you you have? 

Thanks,

Dan

An interesting topic and you are realizing that dishwashers wear out glazes. A simple test I have seen using a decent gloss meter and many washings over time revealed, well just that, the dishwasher wears them away. One interesting conclusion was that more durable glazes existed within a particular R2O: RO range so I am not sure what UMF standard you are applying. Can you clarify what is your understanding of a durable composition? I may be able to help a bit in that respect.

Still your question is highly pertinent in that what is dishwasher safe exactly?

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A couple years ago a friend of mine tested the Licorice glaze from Mastering Cone 6 Glazes with the 5% soda ash simmer test. The gloss level of the glaze changed. My friend emailed Ron Roy with pictures of the before and after results.

Ron Roy's response: "Thanks for this - I'm sending a copy to John along with the pictures.
He will know if we ever tested Licorice so we can confirm your results.
Always interesting in hearing about our glazes. I'm don't think it will be possible to reformulate that glaze to do well in an alkaline situation. Just too much colouring oxide.
Do you think it would show up in repeated dishwasher usage? Have you left a tile in a dishwasher?
"

My friend and I both then glazed 2 test pieces, one we left out of our dishwashers and one we left in the dishwasher for a couple months. There was no change in the dishwasher test piece when compared to the unwashed test pot for either of us. We know there is enough silica and alumina in the recipe to in theory make a stable glaze but it failed the soda ash simmer test. Our conclusion was that the 5% soda ash simmer test is too harsh, yes the dishwasher is probably degrading the glaze very slowly over time and repeated washings but no where near the extent that the soda ash test did. 

@DBPottery, if you post your recipe we could see if there is something way out of wack with it. Info about the clay that changed colour. Also some pictures of your soda simmer test and pots that have been going through the dishwasher for years along with a test piece that hasn't been through the d.w. to compare it to. Just to confirm we are talking about the same test, 50 grams of soda ash and 1 litre of water, water level topped up as needed to keep the solution at the same concentration. 6 hour simmer, rinse and dry test piece.

 

Edited by Min
clarity

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14 hours ago, DBPottery said:

I'm looking for some advice on testing pottery for dishwasher safe cleaning. I used the test Mastering Cone 6 Glazes recommends (5% soda ash solution and simmer for 6 hours) and I don't think my results are accurate. Maybe I did more of a boil than a simmer?

Anyways, everything that came out of the test basically lost a good amount of gloss. Why I say I don't think my results are accurate is because the exposed clay portion turned pretty white as well. I have been washing a set of pottery dishes in my dishwasher for about the past 5 years and the exposed clay portion on the bottom of that ware is no where close to what my results look like with the Mastering Cones 6 Glazes test. Also, I tested some recipes they provided in their book and did a whole lot of work with glaze calculation software to get the percent makeup of materials as close to their Unity formula and they said they considered these glazes durable. So, I find it hard to believe what I did was correct, seeing everything else I've followed from that book has been spot on with getting the same results.  

I'm trying to figure out if I did something wrong or if the test isn't that accurate. What advice you you have? 

Thanks,

Dan

Just to add, it’s really really hard to create a test that predicts future outcomes. The creators out of an abundance of caution and unknown predictability often try and determine what is likely a reasonable conservative approximation. Absent waiting many years the test usually provides some guidance on what can happen worst case. I am with @Min in posting the recipe. I am curious what UMF guidelines it adheres to.

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Thanks for the replies. Yes, we are talking about 50 grams of soda ash to 1 litre of water, water level topped up as needed to keep the solution at the same concentration. 6 hour simmer, rinse and dry test piece. I'm just looking to make sure my glazes are food safe. This is my first stab at trying to make my own line of glazes. I've been having too many issues with commercial cone 6 glazes (crazing mainly). I have been using the Master Cone 6 Glaze recipes for all my testing. I modified the unity to get my current day materials to be the same makeup as what was used in Mastering Cone 6 Glazes. I have made sure to stay within their recommend limits as well. My middle test tiles in my picture below with 3 colors is actually Licorice, so the fact you tested Licorice and felt the soda ash test was too harsh is lining up with my thinking. 10 out of 11 of the glazes I tested in this group passed the 3 day vinegar soak as well, the one in question probably passed but I feel like I little bit of loss in the gloss, but almost arguable if it's just the way the light hits the test tile at the grove from my fingers on the wheel. 

The clay I used in the picture with 3 colors below is Highwater's Red Stone with my own mixed up glazes (recipes included below as picture). The soda ash test is on the right test tile and the non-tested sample is on the left. Notice the clay portion of the sample on the left is a much more defined brown.

IMG_0893.jpg.1f34d0c7bbaa5f1ee42d0ac24e558101.jpg

IMG_0895.jpg.ed4a7927bcaa822cb58be4c50883b9e5.jpg

IMG_0894.jpg.23e79f18a47d765a639289ce6bc056cf.jpg

IMG_0896.jpg.d3527409e4aec603401d01d8f5759397.jpg

Below is a bowl that has been through the dishwasher for years. The clay I used in the picture below with the blue bowl in my hand and bottom of a vase is Highwater's Speckled Brownstone with a commercial glaze (Mediterranean Mist from Standard Ceramic). This is part of the reason I'm not making my own glazes. This dinnerware set crazed and I have come to find out that I really needed to fire to cone 6, not cone 5 for vitrification of that clay. Given this, the years in the dishwasher has not done much to them. The bowl in my hand (left) has been through the dishwasher many times and the vase (right) has just been sitting on the counter. I wish I had another bowl to compare, but I don't have one that hasn't been through the dishwasher.

IMG_0897.jpg.70437f6a53b680c13430338b867179ad.jpg

Thanks for the help. 

Dan

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Nice lookin stuff!

First to dishwasher safe, dishwashers wear out glazes in general far more than vinegar, not sure where the vinegar thing started. Dishwasher safe is an odd designation in my view. Even though they wear out glazes the amount a bad glaze wears in comparison to human time is another debate so when we speak of degradation with respect to gloss it is just that or a percentage change which doesn’t mean that percentage of glaze wore away. Nor is it an indication of potential leaching. So why do I bring  this up? Because there are really not great quantifiable studies on the many many glaze combinations used. Having said that there is some excellent gloss degradation research that reveals an R2O:RO of O.3:0.7 is a durable sweet spot. 10% outside this range and durability in gloss testing falls away greatly. High R2O’s are even worse so we generally view anything from 0.2:0.8 - 0.3:0.7 as likely durable if it fires and fully melts. Outside those values we know that the gloss degrades with each washing. This is a bit controversial for some but is the simplest thing I have seen to indicate a glaze is likely durable or not.

wow,  a mouthful!

Food safe - food safe is defined as no cadmium or lead so that is an interesting narrow definition as well. No cadmium or lead  you are good to go.

Microwave safe - who knows!  basically low absorption, maybe no metals

so for your glazes by recipe,  here they are in Stull and  some general thoughts. Lots of debate here on this perspective so I hope you take it as presented.

 

Next up, Licorice

R20:RO really nice! Probably fires more matte on its way to becoming underfired and has a touch more boron than we would like, but not bad. Really like the R20:RO though so as long as this fires as it’s chemistry says, I think likely durable

DBDFBBF8-A2C6-47C4-ADEB-8A19C6318943.png.e1f40317b3441cba268ed71a8f50a44c.png

Finally sea mist2

Nice R2O:RO, spot on with boron, decent location in Stull. As long as this fired gloss I would find this likely durable.

835969AF-D4A6-4AD1-8D05-63EE8CADA00E.png.9db5fe6fb4715ef13ac0d0aac898ff4c.png

 

Even those outside the magic flux ratio may not wear away in my lifetime actually, just lose their gloss more. I like your approach, being cautious and trying to prove to yourself with some testing it likely is reasonably durable. Glazes that dissolve in vinegar or wash away in 20 dishwasher cycles are obviously not good, even without lead or cadmium.  I am not sure a mouthful of silica is something I want to sell though even if it’s technically food safe.

The R2O:RO tests were done over a long period of time using real  glossmeters so In my view they have some tested measured validity (gloss degradation validity)  and it’s pretty easy to adjust the flux ratio of my glazes to get them in a more ideal range so why shouldn’t I do it?

Not sure that helps but it is a perspective of a difficult subject.

 

Edited by Bill Kielb

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23 minutes ago, liambesaw said:

Vinegar or lemon test is done because most foods and drinks we eat are acidic. At least that's the idea about it.  

Your glaze generally doesn’t care, the dishwasher erodes the glaze a bunch. Vinegar still  not a very good indicator.

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@Bill Kielb Thanks for the compliment. I've gone through a couple hundred test tiles to get to about 10 I'd like to move forward with for a set of colors. The extra prospective is nice, as I've had to teach myself all this stuff from the ground up. Thank you so much! The R20:RO is new to me, so I did a little research and it's one more tool to add to the bag. I found the spreadsheet you used as well online. 

It appears the spreadsheet you used only takes the base glaze into consideration? In other words, any colorants do not affect the calculations? 

Dark Sky Blue and SeaMist2 are both the same base glaze, so in the spreadsheet if it doesn't take colorants into consideration, your comments about Sea Mist2 also apply to Dark Sky Blue. 

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46 minutes ago, DBPottery said:

@Bill Kielb Thanks for the compliment. I've gone through a couple hundred test tiles to get to about 10 I'd like to move forward with for a set of colors. The extra prospective is nice, as I've had to teach myself all this stuff from the ground up. Thank you so much! The R20:RO is new to me, so I did a little research and it's one more tool to add to the bag. I found the spreadsheet you used as well online. 

It appears the spreadsheet you used only takes the base glaze into consideration? In other words, any colorants do not affect the calculations? 

Dark Sky Blue and SeaMist2 are both the same base glaze, so in the spreadsheet if it doesn't take colorants into consideration, your comments about Sea Mist2 also apply to Dark Sky Blue. 

Most colorants have no major effect on the durability or melt of a glaze because they're in such small amounts.  Ones to be careful of are iron (strong flux in reduction) and zircopax (extremely refractory), so if you see those in amounts over 5% they may affect the melt. (Really any colorant over 5% is overboard)

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57 minutes ago, DBPottery said:

@Bill Kielb Thanks for the compliment. I've gone through a couple hundred test tiles to get to about 10 I'd like to move forward with for a set of colors. The extra prospective is nice, as I've had to teach myself all this stuff from the ground up. Thank you so much! The R20:RO is new to me, so I did a little research and it's one more tool to add to the bag. I found the spreadsheet you used as well online. 

It appears the spreadsheet you used only takes the base glaze into consideration? In other words, any colorants do not affect the calculations? 

Dark Sky Blue and SeaMist2 are both the same base glaze, so in the spreadsheet if it doesn't take colorants into consideration, your comments about Sea Mist2 also apply to Dark Sky Blue. 

A colorant spreadsheet is in progress and being researched as to how it might fit in Stull. Stull seems reasonable for establishing texture / gloss and general regional characteristics of a glaze which is actually a game changer. While not intended to be exact, if your glaze should be matte and fires matte, life is likely good. If your glaze in Stull is gloss and fires matte, its likely underfired. A simple point but actually very useful as when I ask folks what should be gloss and what should be matte there are many answers including if I slow cool some glazes they will look matte, which is true but not a particularly useful tool to tell if the glaze was likely fired to maturity.

Lots of room for research with glazes. The more the merrier.

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9 hours ago, Min said:

pssst, Bill, first ingredient in the Dark Sky Blue glaze recipe from Dan is G-200 EU @ 20.8 not Gerstley Borate.

Man, cutting, pasting, posting, shrinking this is tough stuff!  Fixed as promised ( @DBPottery )I hope!

Dark Blue sky:  decent R2O:RO, decent boron, nice location in Stull and it fires the way we think it will, glossy, not too glossy at cone 6. What's not to like!

767007671_DarkBlueSkyFixed.png.3433e95e1851aabf1a6fd93fbbf41c8b.png

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10 hours ago, liambesaw said:

...any colorant over 5% is overboard

zircopax is technically an opacifier and becomes most effective only after 4-5%

iron saturates and tenmokus, in my experience, typically require amounts greater than 5%

 

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Yep, and they have an effect on the melt at those levels, but they also dont really matter as far as food safety goes. I was speaking mostly about the ones of concern like copper, cobalt, manganese

Edited by liambesaw

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19 minutes ago, liambesaw said:

Yep, and they have an effect on the melt at those levels, but they also dont really matter as far as food safety goes. I was speaking mostly about the ones of concern like copper, cobalt, manganese

Just to add if something doesn’t melt fully, for whatever reason,  it likely  affects glaze  durability.

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On 10/2/2019 at 12:11 AM, Bill Kielb said:

Your glaze generally doesn’t care, the dishwasher erodes the glaze a bunch. Vinegar still  not a very good indicator.

It depends on the makeup of the glaze itself as to how either an acid or an alkaline environment will react with it. This is why both an acidic test plus an alkaline one are recommended. With an acid attack on the glaze the alkali ions in the glaze are attacked opening up the glaze to degradation. 

http://www.qualicer.org/recopilatorio/ponencias/pdfs/0063301e.pdf

https://books.google.ca/books?id=Qq3zCAAAQBAJ&pg=PA560&lpg=PA560&dq=acid+and+base+alkaline+attack+of+ceramic+glazes&source=bl&ots=xK8_GiGYgj&sig=ACfU3U0l0V0u1mf524UvWCRrItZgkMBARA&hl=en&sa=X&ved=2ahUKEwiElduFvIDlAhWY4J4KHY2FAP04ChDoATAAegQICRAB#v=onepage&q=acid and base alkaline attack of ceramic glazes&f=false

http://www.thaiceramicsociety.com/download/Chemical_resistance_and_cleanability_of_glaze_surface.pdf

 

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7 minutes ago, Min said:

I’m good with both tests, as to 24 - 48 hr. vinegar being the durability decider as many have been taught I still contend that the dishwasher is a main cause of glaze degradation just by sheer frequency in a pots lifetime.  So the message is: for durability, surviving overnight vinegar or lemon really is not indicative of what will likely wear this away through its life nor would an abbreviated alkaline test likely be  reasonably indicative.

The implication to me is strive to make durable glazes when practical.

Food safe is a whole other mess of sorts of course. Dishwasher safe, my dishwasher is safe from almost everything it wears away at each washing cycle.

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4 hours ago, Bill Kielb said:

 as to 24 - 48 hr. vinegar being the durability decider as many have been taught 

I'm curious if that's the theory most potters take. I don't think of the vinegar test as being the durability decider at all. I view it as a way to rule out glazes rather than rule them in. If it fails the vinegar test then it's a no go as as a durable non leaching glaze, if it survives the vinegar test then the potter can go on to do further testing (dishwasher and lab) if they feel it's warranted. Vinegar (or lemon/lime) test is fast, economical and easy, I think that's why it's used to rule out glazes.

 

Edited by Min

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21 minutes ago, Min said:

I'm curious if that's the theory most potters take. I don't think of the vinegar test as being the durability decider at all. I view it as a way to rule out glazes rather than rule them in. If it fails the vinegar test then it's a no go as as a durable non leaching glaze, if it survives the vinegar test then the potter can go on to do further testing (dishwasher and lab) if they feel it's warranted. Vinegar (or lemon/lime) test is fast, economical and easy, I think that's why it's used to rule out glazes.

 

Maybe, have not really met many with that outlook but that would be a good way to view it.   It’s quite common that I hear well it didn’t pass the lemon  test so I will just use it for the outside of things.

I can honestly say though that I cannot remember when someone said that it passed the lemon test, now time for more testing! LOL

Hope so,  potters are getting more sophisticated about chemistry, longevity, etc...

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21 hours ago, Bill Kielb said:

Man, cutting, pasting, posting, shrinking this is tough stuff!  Fixed as promised ( @DBPottery )I hope!

Dark Blue sky:  decent R2O:RO, decent boron, nice location in Stull and it fires the way we think it will, glossy, not too glossy at cone 6. What's not to like!

767007671_DarkBlueSkyFixed.png.3433e95e1851aabf1a6fd93fbbf41c8b.png

@Bill KielbThanks! I know it's a lot of work. I've put so much time into these glazes to make sure they work and I'm glad to see it's paying off. I got as many of the individual materials analysis as I could, which was a real pain. Entering all the info is so time consuming and it has to be spot on or the output will lead you in the wrong direction. Getting up to speed on a topic I never thought I would get into has been satisfying. 

Edited by DBPottery

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4 hours ago, Min said:

I'm curious if that's the theory most potters take. I don't think of the vinegar test as being the durability decider at all. I view it as a way to rule out glazes rather than rule them in. If it fails the vinegar test then it's a no go as as a durable non leaching glaze, if it survives the vinegar test then the potter can go on to do further testing (dishwasher and lab) if they feel it's warranted. Vinegar (or lemon/lime) test is fast, economical and easy, I think that's why it's used to rule out glazes.

 

That's what I'm trying to do. I want to make sure a glaze is good with simple tests I can do and then pay for lab testing. I'd hate to pay the lab testing fee for a glaze I could easily find an issue with on my own.

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1 hour ago, DBPottery said:

That's what I'm trying to do. I want to make sure a glaze is good with simple tests I can do and then pay for lab testing. I'd hate to pay the lab testing fee for a glaze I could easily find an issue with on my own.

Gloss meter and persistence is definitely doable. Lab tests get expensive and you likely have to order something other than cadmium and lead which you pretty much know is not in your glazes already. Durability and RO is about the best I see at this point. Leaching from oxides becomes a permissible level thing and whether one can actually consume enough to reach the limits.

The Katz spreadsheet is pretty rough in its basic form, I added some simple VBA code and some colorant research and a chem research tab. we have his permission to redistribute with the changes. I made it a five tab and just do a single glaze at a time with four trials. Also allows copying one glaze forward to the next trial so helps with the typing a bit. I use it for quick simple analysis. The chem research tab allows you to quickly filter and sort. It’s fairly useful and as we improve the worksheet I send out the updates to about 20 folks who have opted in.

Message me if you are interested and we will figure a way to get it to you.

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