Hulk

https://lindabloomfield.co.uk/  ?

Joe at Old Forge Creations is also a UK potter who’s been doing a lot of work in the glaze community, and he does make himself available for some questions. He’s on Glazy and Instagram.  I spoke with him, and he said he uses North American materials, which he says should be available, and he found the cost savings in converting recipes to UK materials to be negligible. He also recommended Linda Bloomfield as a resource if you wants to start with more locally based recipes.
Joe has a big presence on Glazy (search Old Forge Creations), but his blog post on his First Five Ingredients glaze is here: https://www.oldforgecreations.co.uk/blog/first-five-ingredients-where-to-start-with-glaze-making. There are links to purchase materials for both UK and US sources.
At a quick google search, I can’t find a website for Linda, but she has a significant profile on Glazy, and many published books and a youtube channel. 

Hi and welcome!
Gerstley borate is a great standalone brushing medium and would be added to iron to help make it more workable, and to dilute the amount of oxide you’re using. (Some oxide is good, too much can cause glazes to crawl over it.) I find iron mostly doesn’t need help fluxing, but other oxides may.
if you want a green wash, don’t use the nickel. It tends to go brown.  Copper carbonate benefits from some kind of flux with sodium in it to help turn it green. GB does have some sodium, but if you try it and find it isn’t enough, try mixing equal parts epk, copper carb and any Ferro frit you have to hand. 3110 would be ideal, but 3195, 3134 and 3124 would also work. The epk will help make this mix brushable and dilute it, and the frit will do the flux/colour change part. 
 

Hi Kennedy,
Welcome to the Forum!
Are you glazing the insides (liner glaze)?
A good liner glaze should melt well; not craze (crack); come out be smooth and shiny (easy to clean); not cutlery mark (again, smooth and shiny); stand up to wear, tear, acids and alkalis; and not leach colorants.
Typically, advice for functional ware includes choosing a clay that has very low absorption when fired to its target cone, around one percent absorption or less.
Still, a sound liner glaze, no cracks, no pits or holes, should hold water!
Hope that helps.
If you are glazing the outside only, then expect water to soak into the clay, saturating the entire piece!
The exceptions would include clays that are fully "vitrified" - that do not absorb any water.
Can you post images of the liner glaze and the recipe/formula as well?
 
liner glaze
Liner glazes (digitalfire.com)
Functional glaze
Functional (digitalfire.com)
See the links to vitrification and maturity at the bottom of the article.

My local supplier had limited supplies during  Covid, the one employee almost died from it.   She was in the hospital for a month,  they sent her home to  put together estate plans.  They said they could no longer help  her.   She laid in bed for 3 days and decided to get up and clean her house,  she is back at work lifting those heavy boxes of clay.    The store seems  to be well stocked now I think it is because Virginia is back.  Denice

With all of the consideration about supplies and material costs along with the past of Covid effects on business. . . I have wondered how your go to supplier is surviving. I was at SC in Pittsburgh last year and noticed how much they seemed at the time to be down on stock. I also have noticed that a supplier I had seen out east of me has not seemed to be open when I have been by.
QotW: Have you found a tightening of suppliers in your area or a shortage of supplies at your GO-TO Ceramic supplier?
I have been interested in making a trip to Bailey up in NY, but don't look forward to the drive. Used to swing by there on the way back from a vacation years ago. The new kiln came with 6 half shelves, but I would like at least another pair for firing patens, even two more pair would give me a decent glaze load pack. However, with NCECA coming to Richmond next year, I can take a hold til then.
 
best,
Pres

I'm using Weebly/Square, where I'm posting some "about" my work, images of current and historical work, blog entries, contact info...
It's not perfect, but it is fairly easy to use and maintain.

Penetrating oil, liquids that dissolve corrosion/rust (e.g. LiquidWrench) can be helpful, again, depending.
Judiciously applied heat can be helpful, again, it depends!

Thanks for the great ideas….. hopefully at least one will work, for me.
Cheers
Mike

Testing/proofing on test tiles, small slabs, et cetera, time permitting ...afore committing a large piece.
How many words are you looking to depict? A phrase, a stanza, the entire lyric?

I think we are overcomplicating this.
If glaze is fine then don't mess with the TC offset. If bisque is under-firing then either fire to one cone hotter if using the preprogrammed schedule or increase the final temp like Neil said. Given that ^07 is barely bending and you are aiming for ^06 then try firing to preprogrammed ^05. Approx 30C between 07 and 06 and 06 and 05.

I thought they had stopped making it but potclays seem to have it in stock. https://www.potclays.co.uk/calcium-borate-frit I feel like it has doubled in price but I haven't bought any for a long time. 
If you want to look into making glazes start with limit formula https://digitalfire.com/article/limit+formulas+and+target+formulas
 

That should have gotten you to cone 06, maybe even cone 05. It's really more important that it's firing accurately at glaze temps, which it is, so I wouldn't make any changes to the thermocouple offsets. I would just adjust the final temp up 30-40 degrees.

https://ceramicartsnetwork.org/ceramics-monthly/ceramics-monthly-submissions/ceramics-monthly-submission-guidelines#article-3
https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-submissions/pottery-making-illustrated-submission-guidelines

Here are the documents that came with the wheel. I don't remember how or where i bought this wheel but I'm sure it was in 1973.

Testing/proofing on test tiles, small slabs, et cetera, time permitting ...afore committing a large piece.
How many words are you looking to depict? A phrase, a stanza, the entire lyric?

Testing/proofing on test tiles, small slabs, et cetera, time permitting ...afore committing a large piece.
How many words are you looking to depict? A phrase, a stanza, the entire lyric?

You didn't mention how much time you have to pull this off. You will need several tests and trials, from start to finish, before you are likely get a result that is what you intended and (or) that you really like.  So, I'd want to be sure I had enough time to deal with the inevitable process of getting from point A to point B, including set-backs. Time is especially important if it should turn out that  there is a need to switch gears and design something else. Just something to think about--how much time is available to explore & produce to your satisfaction. Just FYI, Sanbau Studio offers underglaze transfer papers (lettering sets) for ^04 to 10...maybe someone else here has some experience with a transfer method...tho it would probably not be something to use for a lot of text.

If you use a claybody made for tiles it will be far less plastic than your typical claybody, less plasticity in a claybody helps tiles stay flat. (along with the practices you are already doing and @akilpots suggestions) Also, if you lay a piece of very thin plastic sheeting/film over the clay before pressing the cookie cutter down it will round over the edges so you don't need to smooth the topside eges of the coasters. 

i dont make coasters but i do make tiles sometimes so these tips should apply...
make slabs of stiff leather hard clay.
you can dust the inside of the cookie cutter with cornstarch to help each piece release.
make sure you are drying them out somewhere with no drafts. you want each one to dry evenly so like not having the left side dry faster than the right side.
the less drying they need to do when cut from the slab the better chance you'll have at them staying flat.

Maybe pictures are here

I just had a minor flood last week in my garage, ( blocked drain) and my Brent wheel would not stop.  I took the bottom plate off the pedal and saw some moisture.  I blew it dry and tried to adjust it and it wouldn't stop spinning.  Spent hours on line searching for answers, saw high prices. My wheel is a Brent CK (a kit I think) and is at least 50 years old although not used for 3 decades so I was getting resigned to spending $600 to fix it.  I tried adjusting the pedal one more time and it works now. Phew.  It is a great wheel.

Just when I think I have seen it all; most of it anyway. I fired the above shown sample to cone 04, and was surprised when I opened the kiln. The new sample is on the left, and a standard terra cotta on the right. From the deep color (reddish/orange), possibility that this sample might have limonite in it. Limonite ( natural yellow ochre), which would account for the deep color hue. Wild clay can get wild, even for those that are familiar with it. This sample will certainly go to the lab for analysis. Not cracked it open yet to check for black coring, but I suspect there is. I dipped both in water for a quick absorption test. The terra cotta drank it up, and the limonite? sample did not. 
Tom

Testing/proofing on test tiles, small slabs, et cetera, time permitting ...afore committing a large piece.
How many words are you looking to depict? A phrase, a stanza, the entire lyric?

As for decoration, have you ever thrown a cylinder, then decorated it by either stamping, or incising then shaping the cylinder into the shape you want?  I find this a very satisfying way to work, and if you have letter stamps, or a decent script hand you can work wonders with phrases in the clay. Then after bisquefire before glazing you can use a stain/underglaze to work color into the script and wash off the high areas. This will allow the decoration to show up under glaze layers if the glaze layers are thin enough and not too dark in color. Check out some of the posts on my blog site. . . listed in my profile.
 
best,
Pres