What To Use For Marking Bottom Of Glaze Tests

[yappystudent]

My personal thought is just a contrasting color slip, is this right? Black slip for light color tile, and vice versa.

 

Redoing all my old shard tests because they are just a mess, I've made tons of small tiles in the clays I like best so far, and they are now bisque fired.

I've already carved in info as to what type of clay each test tile is made out of on the backs, now I need to mark each one after apply the glazes with code for the glaze type I'm using. The tiles are all the same shape/size. Although I'll take pictures of them first, they are so alike in shape/size I'll forget and get them mixed up, I can't just use a sharpie after. This sounds simple enough but I'd intended to use red iron oxide but red in the forums here it can rub off even after firing and I would rather avoid hunting down arcane substances to mix it with to make it permanent.

 

The pottery store owner suggested black underglaze but I'm not sure he understood exactly what I was saying, won't that stick to the shelf during a glaze fire if it's on the bottom of a test tile?

 

Any advice would be helpful, thanks!

[Joseph Fireborn]

I use 50% RIO 50% Gerstely Borate. It will not rub off after a glaze firing, however it will stick to a shelve if you put it on thick. I usually just label the tile at the bottom of the tile. 

 

This is what RIO/GB mix looks like: 

 

 

After I pull out the tile which is numbered and wrote down in a notebook. I then take pictures of all the tiles and code them in insight live. I used to not do this, but I started losing my notebooks and not knowing which glaze, how many layers, or what glaze combinations a tile was became really really annoying.

 

Now I put the tile picture in the recipe file inside insight.

 

I have also used underglaze pencils, but I find its much easier to just brush on RIO. 

 

Underglaze pencil on porcelain: 

 

 

The pencils are pretty hard to write with imo. I wasn't too happy with it.

[Magnolia Mud Research]

I use a mixture of red iron oxide and maganese dioxide about half and half by volume and suspend it in water,

sometimes with a pinch of ball clay to keep in suspended. 

Or make a paste and treat it like a pan of watercolor.  Wet brush with water, load brush from pan, apply to tile.

Apply it with a fine watercolor brush. 

fires into the clay body at any temperature from bisque firing to cone 10.

Does not fuse to kiln shelf. 

 

LT 

[oldlady]

black underglaze should work fine without sticking.

 

if you simply number the test tile while it is still leatherhard, use a small ball stylus, the second small size works well, press in enough to make a deep enough mark and number the tile.  once it is fired, the small, fine point sharpie will fit into that groove and be visible at a distance.  

 

then you need a way of recording what the number is.  i use a paper notebook, would hate a computer.  but, you might like to use a computer.  this works well for me because i only use one clay body.  if you use more than one, the simple addition of a letter will differentiate the body color.  plain number = clay body one.  letter A before the number  = clay body two.

[Marcia Selsor]

I use black under glaze pencils or a wash with heavy iron. I prefer the pencil.

 

Marcia

[Pres]

I number my test tiles for each batch before bisque with an incised letter and number. I have a set number of glazes, and do not make a whole lot of changes. I have been working on the perfect white for quite a while, and have 3 batches that I have running right now. Each has a little different characteristic, opacity, breaking movement, color, clay color reaction. The search for this came with my switch to the Hazelnut brown of SC, from the manganese speckled. Both of these are cone 6. My favorite white at this moment seems to be a combination of opacifiers instead of just one.

 

 

best,

Pres

[neilestrick]

Underglaze pencil.

[Mark C.]

underglaze pencil

[yappystudent]

ty ty. BTW I did mention they are already bisque fired and I did carve in some information while they were leather hard, but I appreciate the help anyway. I'd have to pick up a few supplies to try most of the suggestions given but they seem like great ideas in future, especially the pencils.

 

*Joseph F, if you're still following this thread what app is insight? Is it free and what does it do, and is it just for smartphones? Just curious, all I have is a stupid phone atm and shall remain thus for some time. So far I just keep my ceramic notes on openoffice documents, of which I have a lot and they're pretty disorganized. In fact I see a new thread topic in this...

[Joseph Fireborn]

https://insight-live.com/index.php

 

 

It is the technical part of digital fire. You can store information about glazes and many other things as well as change recipes and look at the chemistry involved in them.

 

It's certainly affordable as well. I think I pay like 30 a year for membership. I'm not sure since I haven't paid yet this year. Still going off last year.

 

And I don't use my phone for it. Just use the browser version.

[Min]

Dixon high heat china markers in brown are good to at least ^7. They leave a bit of a waxy finish so don't smear if you sponge the bottom of the test tiles. Way less expensive than underglaze pencils. They have a paper strip that you peel away instead of sharpening them, lasts for ages. 12 pencils for around $8- on Amazon. Staples used to carry them also, don't know if they still do.

https://www.amazon.com/Dixon-Peel-Off-Pencils-12-Count-00095/dp/B002JG9NA6/ref=cm_cr_arp_d_product_top?ie=UTF8

[yappystudent]

Good info, thanks again

[perkolator]

We use an iron mix similar to the 1st suggestion, only ours has some clay added in there.  It's not equal parts like an underglaze, it's more like 3 parts Iron, 2 parts flux (Gerstley borate) and 1 part clay (EPK) for suspension.  Use CMC gum solution instead of plain water.  Adding manganese dioxide will make it more black vs iron red