How do you get low fired matt glazed dinnerwar resisting to cutler marks?

[Alyaa]

Hi I have a problem I bought porcelain plates fired only at 1200 degree centigrade as per my request inorder to be a little pourous to accept the glaze and then fired the glaze at 1060 C as recommended for it , the results of the pourousity test was 3% and when I tried using a knife on the plates it caused a scratch and I am really depressed as I spent a lot of money for these plates I don’t know what is wrong is it the glaze is not yet mature or the clay is not yet mature?

[liambesaw]

Sounds like an odd firing schedule... Bisque to cone 5, glaze to cone 06.  I'm guessing it's a cone 6 porcelain.  If dinnerware is marking on it, it's a glaze issue.  I'm guessing a low fire matte glaze?

[Alyaa]

Yes it’s low fire matte glaze OMG how did you know! and it’s cone 12 porcelain actually I fired glaze for 4 hrs only and I didn’t hold at the desired temperature I just turned the kiln off once I reached the temperature 

[neilestrick]

Matte glazes will often scratch unless they are properly formulated. A matte glaze that scratches easily is probably also the type that will not clean very easily, so there's a hygiene issue there. There's also a good chance that the low fire glaze is not going to fit well on a cone 12 porcelain. Is it crazing? Glaze fit is very important on low fire work because if the glaze crazes, liquids will seep into the wall of the pot, where it cannot be removed, and can grow bacteria.

Since your plates aren't really useable as is, I would go ahead and fire them hotter and see what happens. At some point they may become useable once the glaze melts enough.

[Alyaa]

Do You  mean to fire the glaze hotter than they should be and observe the result ? Or to use high fire glaze?  and is this defect often happen with most of matte glazes or only with low fire one?

[liambesaw]

Depends on the mechanism of matting.  If it's a commercial glaze you should contact the company which makes it and ask whether or not the glaze is cutlery marking.  I just avoid matte glazes on surfaces that will contact mouth or food, easier to clean and care for.

[Alyaa]

Thanks a lot you were very helpful but what I really want to be sure of if I fixed the glaze type and temperature, Are these plates that were under fired could be glazed and used as it will be big loss for me?

[neilestrick]

Fire one hotter with the glaze that's on there and see what happens. Put a waste slab underneath just in case it runs.

[Alyaa]

Thank you all I will try and see.

[Bill Kielb]

Cutlery marks are generally a result of a hard rough surface wearing away the cutlery. Zirconium silicate (Zicopax)  whites generally can cutlery mark as well for the same reason.  Microscopically these surfaces are sharp and very hard so they wear away a bit of the cutlery. With respect to absorption, firing a cone twelve clay to maturity or near maturity would be the best way to minimize it.

if you are ok with 3% absorption but just want to re glaze with a gloss lowfire glaze, you could try that. It probably has minimal risk, might solve your cutlery mark and in the end maybe decrease your absorption a bit. Many lowfire glaze potters layer. There is some limit to refires though, can’t do it for ever.

I mention Zirconium based white, because even though it will appear gloss, zirconium glossy glazes can mark as if they are rougher because the zircon does not melt and is rather rough microscopically.  So glossy glazes can be rough and cutlery mark as well.

[Alyaa]

Thanks for valuable information I will try to change for higher fire glazes, hope to make it harder and more mature.

[hitchmss]

https://digitalfire.com/4sight/recipes/cone_10_silky_dolomite_matte_base_glaze_39.html

https://digitalfire.com/4sight/glossary/glossary_cutlery_marking.html

Some good information about high fired, silky/matte glazes which dont cutlery mark or craze. If you're learning about glazes & faults, Tony's website is a WEALTH of wonderful information!

[Alyaa]

Thanks so much I really appreciate that from you 

[S. Dean]

Just a caution that you should consider all these suggestions as possible pathways that need to be tested.  You are in unknown territory so pick one approach that you want to try, test it on one piece to see what happens.  That way if the test doesn't work, the whole set isn't affected. 

[Alyaa]

That’s what I am going to do after I read these links starting by 1 piece in every trial, thank you all you are amazing .

[oldlady]

alyaa, please be kind to any new people who might benefit from reading your question and change the title to reflect what you are talking about.  forget the word "help" because it is not descriptive of the topic.

[Alyaa]

Ok dear, I changed the title and I really got many benefits from this talking.