GEP

I used to use Frit 3134 as a substitute for Gerstley Borate back in the 80's when there was a Gerstley Borate shortage. I found it flocked my glazes the same way Gerstley Borate did. I concluded that there must be enough free Boron because of the low Silica and Alumina content in the formula that it remained soluble. Boron is a glass former. Anyone who has thrown Borax on a raku pot and found it created a beautiful glassy glaze has seen it in action. Overtime the glaze will desolve in water alone. I have a potter friend who used a beautiful clear glaze she was given by a well known ceramist that had way to much boron in it and overtime her glazes deteriorated.
To answer your question Frit 3134 is not a complete glaze. It is used as a flux and needs more silica otherwise the free Boron will soften the glaze. There are a lot of  great cone 6 clear glazes out there and davidh4976 glaze is probably a good one. Frit 3195 is much closer to a complete glaze.

And back to arguing about the Katz documents - all those graphs are based on a flux ratio of 30:70 R20:RO. Stull ran his infamous chart on this flux ratio. There is wide agreement that this ratio is optimal. There is also modest agreement about silica and alumina molar limits of generally 2.5 to 5 for silica and .25 to .5 for alumina for mid fire with a Si:Al ratio of around 7 or 8 being a nice glossy glaze. There is less published documentation showing that when keeping the flux and Si:Al ratios constant, cone 10 melt occurs higher up the diagonal on the Stull chart and cone 04 melt occurs lower down the diagonal. There is also wide agreement that boron is helpful at mid-fire and necessary at low-fire, with the Katz diagram showing recommended molar levels across the range of temperatures. But when we mix all that together and do something different, we don't really have any guidance, so as @davidh4976 just said, we talk past each other. The recipe @GEP is asking about is completely outside of conventional limits . The flux ratio is 22:78 - Katz spoke of not going above 35:65, but nothing about going below, where this one is significantly below the gold standard. The Si:Al ratio is 7.8, nice for a glossy, but the molar levels of 4.1 and .52 are in the cone 10 range. The boron molar level is at .72, a bit high for cone 04 (i.e., off the Katz chart). So what we have is a high calcium semi-matte (based on the flux ratio) with cone 10 glass (based on the silica and alumina molar levels) and cone 08 boron molar levels that comes out a nice glossy cone 6. As @Bill Kielb said, "there are an infinite number of fired combinations to which research could be applied."

@Min et al, I just pulled the tile after 24 hours half submerged in 30%* cleaning vinegar. There is no change in gloss or color (we use this glaze with a bit of copper and some tin/zirco for a nice turquoise). I will go shopping to find some plain lye (Drano brand has other stuff in it) - when home-brew testing, I like to hit the sample tile with something stronger than kitchen cabinet chems (since I run my dishwasher so infrequently, it would be next year before I would complete the Katz-recommended 30 cycles...).
*Grocery store vinegar is diluted to an acidity of 5% - sometimes. In recent years as manufacturers everywhere try to reduce costs by invisibly reducing quantity in the same package, some grocery vinegars are now 4%. That might not make any difference in your oil and vinegar salad dressing, but if you like to make your own pickles, you need to check the label and make sure you are getting a 5% vinegar. And there, I did it again, took the pottery discussion in another direction. Now we can share recipes for pickles...

Would love to hear how it did in your test!

Mea, this is a interesting recipe that shows up in a variety of places. The version you have is very close to one that we have been using in the Audrey Moore/Wakefield (Ffx County Parks) studio since forever.  That one is Gerstley 50, EPK 17.5, Silica 32.5 (our Gerstley vs. your 3134, about the same effect; your EPK and silica are reversed from ours). From a chemistry standpoint, the massive amount of Gerstley or 3134 generates so much boron that it could/should be a low-fire glaze - and indeed I have seen it in published collections of earthenware glazes. At the same time, the alumina and silica levels are quite high, and so the glaze is robust enough to survive at cone 6. With the demise of Gerstley, I am reformulating it to use 3134, and my revised recipe becomes similar to yours. Something to consider - 30 EPK is a lot to have in a recipe, and will cause issues with shrinkage and cracking (leading to crawling during the firing) so replace half of it with calcined EPK. It just so happens right now I have a test tile with my revised recipe soaking in vinegar, so I will come back in a day or so with the outcome of that.

Plastic Vitrox (PV) version of GB1 using Fabi Talc. (why do I keep thinking that as Fabio talc? lol)
I know PV can vary a fair bit but went with Insight analysis.
Had to supply the calcium from calcium carb in place of wollastonite as the silica was too high using the latter. 

Okay, using Laguna analysis not the Jeff Zamek 2011 article analysis (plus subbing Fabi Talc) I came up with the third recipe below. @GEP, I would confirm with Laguna that info is still correct.
Second recipe is a 1 to 1 swap of both Cornwall sub and Fabi Talc, it needed some tweaking. Laguna Cornwall sub is up but not by nearly as much as with the Zamek analysis, silica is up and the rest just minor tweaks. Again the sodium + potassium is a combined value.
I think Callie brought up a very important aspect, if Laguna is using Custer spar as part of the Cornwall sub blend then this could throw a wrench in the works going forward. Don't know if they use it or not, anybody's guess at this point. 
To keep this from getting too confusing I'll add a PV version in a separate post.

Thanks for the link Mark, the analysis is different for the Laguna blended Cornwall substitute. This could make a difference!
@GEP, I'll redo the recipe using the Laguna analysis. I'll run it with PV also since you have that available too.

True Cornwall has been gone for a long time
The Laguna cornwall blend has been around a long time as well -its breakdown is here
https://www.axner.com/cornwall-stone-laguna-substitute.aspx

Three recipes below, original in the first one using Amtalc since a specific one wasn't specified. Second recipe shows what the formula would look like just doing a direct substitute of Cornwall Stone for the G200 and Fabi talc for the Amtalc. Third recipe is one where the oxides are as balanced as I can get them without adding another material.
Only change to formula in recipe 3 is potassium and sodium amounts are different when looked at separately but equivalent when looked at when the two oxides are combined. (KnaO figure) Given you are testing this for your liner I don't think this will make a difference.
Main difference is far more Cornwall is needed to supply the sodium and potassium than the G200 supplied. This extra Cornwall bumped the overall silica up so that needed to be reduced by subtracting silica. Same for alumina hence the small drop in EPK. Other oxides just needed minor tweaking.
Silica to alumina ratio is the same in 3rd version, COE is pretty close, this will be a minor fraction of a decimal difference, not significant.
I left the total for recipe 3 at 99.30 to keep the material amounts in whole numbers or just going into the tenths.
If you try this please just do a small test amount first, what looks good on paper doesn't always translate to the pot.

After checking this article from digitalfire, it looks like actual Cornish stone stopped being available in 2014 or so, but there are a number of substitutes. So it’ll be worth checking into which substitute this is before deciding on long term availability. Some of those substitutes were made by combining other feldspars and if Custer was one of the ingredients, that could still present a problem. 
In general, Cornwall stone isn’t as strong a melter as feldspar, and a straight 1:1 substitution isn’t going to work well at cone 6. You might need to add a bit more frit, or adjust with a touch of neph sye, depending. Cornwall stone also has some phosphorous in it, which can make for some neat colour responses/reactions. But it can also flocculate your glaze.
Because I think you’re likely not looking for potassium to provide a specific colour response, you could try subbing another feldspar that has a combined sodium and potassium number that’s closer to Custer’s combined values (KNa). The silica and alumina numbers will be less important to match in your substitution candidate, as you can adjust silica or EPK numbers in this recipe to compensate. 

I rely heavily on a deer tail brush as part of my glazing process. They last a long time, but I taught myself how to make them just to make sure I would always have one. I made a video for anyone who wants to learn how, it’s free on youtube.
 

I rely heavily on a deer tail brush as part of my glazing process. They last a long time, but I taught myself how to make them just to make sure I would always have one. I made a video for anyone who wants to learn how, it’s free on youtube.
 

This time last year I decided to pack in my 44 years of Christmas sales at a small shopping center in a small town close to me.  I had made a special locking booth for just this location and the spot was very cost effective. I picked the dates I wanted to be open in December and paid a flat fee of $200. 
Now when I started back in 1979 selling here I was in front of a very busy drug store. I think it was called Value Giant-then it became Payless Drugs for many years and I dealt with the same manager for 17 years. Back then I paid 10% of sales on a trust basis. That store became Rite Aid then CVS. I went thru many a manager and cut it down to a one-time booth fee-if I recall it was 400-600$ for my 18-20 day run in December.
The local Safeway manager at one point asked if I could set up outside his store so that year and for about 5-6 years as was next to the  store exit. This was a busy location and for the 1st time I got some late day sun into the booth as it faces west. The business was always good. Safeway went thru lots of managers and I decided that I had enough as they were always changing the contact. This location was 600$ flat fee but one manager wanted me to move away from the exit to a dead zone. That year I moved over to the local owner’s pet store and I have been in front there for at least 15 years. I cut a deal with the shopping center manager direct and offered $200 flat fee to whatever dates I wanted in December. The pet store does zero advertising and is a local favorite (small town local store) I have 7 signs that advertise my sale on private property around town. The signs  are in key spots around town and also advertise in local paper so the pet store gets my customers and I get theirs it’s a win win. 
 
Last year a few days before xmas I was taking to my sales help and we both decided it was time to pack it in. I told the manager I was done but had another potter in mind to take it over. 
I called him before new year’s about 1 year ago today about taking over the booth and made him a deal he could not refuse. I would teach him how to set the booth up and take it down as long as he takes it all away next year from me to store at his place  (it’s an install that takes a few hours) and it connected to building and I use the power from Pet store for lighting.
I said the booth and racks are all free and that my insurance is paid up for 2023 but in 2024 he would have to get his own. All I asked for was the $200 for booth fee. 
The one big thing was he got long covid in February 2020 and it nearly killed him (he is young guy) Since then he has not sold or made pot and it’s been a long slow recovery.
He works in high fire  reduction fired Porcelain (Dave’s same as me) and he has great work.
 
That all said I gave him a year’s notice. 
Well we just packed up his booth xmas eve as I always have the past 44 years and I did show him how to build it and helped him with details and have showed him the ropes. His 1st sale  at this location was good for him and he’s on his way to making a storage area to get the booth and racks from me this year to keep at his place. 
I was only going to do this teaching once as I have no other person in our area to give this to.
I feel I’m paying it forward and hope he continues on a path to success as I have had at this location. I had built a huge Christmas season of sales and now it’s one less thing for me to do at xmas. 
Now it’s just keeping my 7 outlets supplied at the holiday season and no more retail myself at xmas. 
All part of the slow down plan
Here’s a few photos of His work in new to him booth this past few weeks.

Mea's details are spot on
I use JB weld epoxy and  a  fine nylon line for hair wraps and heavier line to make my hang loops but its really just minor details-I also drill a hole thru center of bamboo to pull  string with the hairs up and make a loop to hang brush then glue the holes shut.
I have about 4-5 kinds of bamboo (I tend to harvet black bamboo for handles) The timber bamboo in photo gets 30+ high and gets water from sink clay  settling tubs then on to bamboo.
Here's a bunch hanging next to sink waiting for glaze day-I do tend to make them larger than hers -larger handles and more skunk hairs
My glazing is lots of loose brush work under glazes like rutile so these brushes get a workout nearly every week or two.
Thanks Mea for posting the you tube. I never had  a mentor on making these just winged it but that process is the same. I really got into it in the  late 80s and 90s. These where made then.
 

I rely heavily on a deer tail brush as part of my glazing process. They last a long time, but I taught myself how to make them just to make sure I would always have one. I made a video for anyone who wants to learn how, it’s free on youtube.
 

I rely heavily on a deer tail brush as part of my glazing process. They last a long time, but I taught myself how to make them just to make sure I would always have one. I made a video for anyone who wants to learn how, it’s free on youtube.
 

I rely heavily on a deer tail brush as part of my glazing process. They last a long time, but I taught myself how to make them just to make sure I would always have one. I made a video for anyone who wants to learn how, it’s free on youtube.
 

Hi folks, sorry things are late for this weeks QotW, but I have been self quarantined for much of the Christmas holiday, things are negative now.
I know that some of you out there make your own tools, and some feel it is time consuming using the time saved with purchased items to make more pots. However, there are some of you that make your own tools, whether it be ribs, throwing sticks, dies or other things. I do wonder though how many of you make your own brushes? In the past (college days) I had access to deer hair, and some other animal hairs as I hunted and knew folks that trapped and had some other types of hair. I began experimenting with rolling the ends in paraffin, and wiring to a stick. Simple brushes, but interesting how course hair and fine hair would give me different effects, They were fun for in-glaze brush work with accents of dark stains or glazes. Their biggest attraction was the uncontrollability as compared to a commercial brush. Yet after a while, it seemed there was little time to make new, and they did not hold up well especially when dealing with some course glazes or stains. 
QotW: Have you ever experimented with making you own brushes? Please elaborate on how you did it.
 
best,
Pres 

When I was part of the Anazazi Research Group we were suppose to make brushes out of Yucca type plants.   You  had to chew on it to get the fine strings you needed.  The first yucca they decided to try was aloe vera,   I am allergic to aloe vera so I was excused from making a brush.   I tried using one that someone else had made,   Didn't go well,  I think something like a Century plant would work better.   Denice

Yes I have made my own over 30 +years-I have deer  hair (and have some elk to try) but most are made from skunk tails. These are cut off road kills and aired out for a year outside hanging. Then I use bamboo from our property-which is cut and dried in the right lengths. I wrap the hairs tight with a string around them and the end is covered in waterproof epoxy and the string is put thru the center and forms a loop on top to hang brush. I have also just expoxeyed the hairs in without the thru string and still use a string loop in small hole glued in tio for hanging as they dry best hanging. I have shown thse in photos before here. These brushes have lasted many decades of heavy use. The skunk hair is course and very durable. Deer hair is finer. I use them on glaze days -at least 6 of them for underglazing.

These are the most “successful Instagram users.” Not to be confused with “successful potters.” You can’t deposit instagram likes in the bank. What looks shiny and pretty on social media can be 100% a facade. 
I know successful potters from my real life, because doing lots of high-level shows allows you to meet the real deals. Some of them are great with social media, some are bad at it, and some of them don’t do social media at all. There is no correlation. 
My advice to anyone who wants to be a serious pro: don’t place any value on social media popularity. Do it for fun, if you want, but that’s all. 

These are the most “successful Instagram users.” Not to be confused with “successful potters.” You can’t deposit instagram likes in the bank. What looks shiny and pretty on social media can be 100% a facade. 
I know successful potters from my real life, because doing lots of high-level shows allows you to meet the real deals. Some of them are great with social media, some are bad at it, and some of them don’t do social media at all. There is no correlation. 
My advice to anyone who wants to be a serious pro: don’t place any value on social media popularity. Do it for fun, if you want, but that’s all. 

It’s called G-Floor, a heavy duty vinyl flooring meant for garages. It has held up very well at the 10 year mark. The only deterioration is some minor buckling around the legs of the kilns, I guess from the heat of the kilns. But overall I am very happy with it. 

@Pyewackette, I drag heavy things across the floor a lot, and it does not scuff at all. 
If I had the choice of bare concrete, I would prefer that. I needed some kind of covering because my basement came with asbestos tiles. Best way to mitigate those is to cover them up. 
I would not put ceramic tiles in a pottery studio. Lots of heavy things get dropped, and the tiles will be cracked in no time. 
I don’t think the G-Floor makes the floor warmer or softer, it’s not like a residential vinyl floor. I wear very cushy shoes to keep my feet happy (brand name OOFOS sandals, designed for runners).
If you have the option for wood or concrete, those would be best. Like others here, you can use foam mats where needed if you need some softness.