Hulk

Found threads here about Wheels, was shopping at the time.
I still appreciate the welcome detailed and helpful info.
From there, started following new content, and also got hits on external and internal ceramic/pottery searches.
Helps to know that the internal search feature excludes threads that have been idle for two or more years. If I want a full search, I'll use an external search engine.

Hi Pres,
To hit this Forum at the top of the return, "anding" the address seems to do it, e.g.
community.ceramicartsdaily and "red clay"
where I'm limiting for only everything with the exact words "red clay" on the site, well that's what I believe happens, lots of hits!
Note that some browsers support the word and, some require the & symbol.
...there were other returns, but the Forum's was first.

Found threads here about Wheels, was shopping at the time.
I still appreciate the welcome detailed and helpful info.
From there, started following new content, and also got hits on external and internal ceramic/pottery searches.
Helps to know that the internal search feature excludes threads that have been idle for two or more years. If I want a full search, I'll use an external search engine.

Found threads here about Wheels, was shopping at the time.
I still appreciate the welcome detailed and helpful info.
From there, started following new content, and also got hits on external and internal ceramic/pottery searches.
Helps to know that the internal search feature excludes threads that have been idle for two or more years. If I want a full search, I'll use an external search engine.

I've used Gillespie Borate for a long time, and it works great. It tends to be a bit stronger than Gerstley, though, so definitely test. I've found about a 3-5% reduction to be necessary in most of my glazes.

Although I've an unopened fifty pound GB sack, am looking forward to adapting to Gillespie Borate and/or frits.
The choice may become simple, as I expect that Gillespie Borate price will (continue to) bloat; it's $90 for a fifty lb sack a'ready*!
...still a bit cheaper than frits, but not by much.
 
*at a "nearby" supplier that I like

When I've used Murphy's soap I used a quite damp sponge and applied on a thin layer. I let that dry then repeat with a bit of light buffing between coats. Keep adding coats until water beads off the surface. I then bought some mold soap, for me it works better. (I used Murphy's on a whole fish once, as the plaster heated up it made a nasty smell of hot stinky fish combined with Murphy's, Can't use the stuff now without gagging a bit, probably too much info)

Wonderful breakdown of a slice of earth, as dug. I very much appreciate comparing the photo to the analysis.
So those white looking bits in the brown ball clay layer, are those shale? 

Picture below has been cropped to fit format: actual clay size is 7” x 4” x 4”. Sample was saw cut and wetted to illustrate layers/ color/ and grain. Sample was flipped upside down to capture color variations. The orange/gold color on top is actually the bottom of the sample.
A wild clay sample can tell you a lot just by looking at it. Obviously this is a sedimentary clay because it has three distinct layers and colors. The bottom layer is thin, and is noted by the cleavage crack at the bottom left corner. The top layer is granular and light orange/gold in color, which denotes the presence of iron disulfide (iron). This sample of iron disulfide is light in color, which means total iron content is in the 3-4% range. As the percentage of iron goes up; the color will become deeper and deeper. Naturally occurring magnetite (iron) usually presents medium to dark gray in clay color. Naturally occurring hematite will present light to medium “reddish” in color, with no goldish hue. Iron disulfide typically has a gold cast because the iron is oxidizing (rust), whereas hematite is not subject to this natural process.
The middle layer is dark brown ball clay which typically indicates the presence of inorganic sulfides from lignite coal particles. Lighter brown color means less inorganic material, and darker brown means more. The exception to that rule is organic particles (humus). If your sample was taken from a heavily vegetated area; then the level of organic (humus) will be higher, which like wise will create a dark brown appearance. How can you tell if its organic or inorganic? First, the collection site: open fields or valleys will have less organic material, and heavily vegetated areas will have more. Secondly, a very simple test: take a small 1/4 cup powdered clay sample and add a a bit of water at a time until it forms a pliable ball. Does not have to be all nice and neat; just pliable. If it is sticky or gummy feeling; organics. If you can roll it between your hands without it sticking or smearing; it is inorganic. Yes, there are exceptions were a sample can have both inorganic and organic materials.
Besides the obvious large particles of shale; did you notice the smaller nodules? There seems to be a heavy population of them in this sample; which means the middle layer has a higher percentage of 20-60 mesh particles. Bad thing? No, it can be used for non-functional, large format pieces. If you are going to make cups and bowls, then these larger particles have to come out. Wet processing will allow the large particles to settle out quickly, or dry processing will require a 60-80 mesh screen. This sample was found in an open eroded ditch in a field, so the color is most likely from inorganic sulfide. The presence of these sulfides also indicates a coal seam is nearby: which I happen to know is correct because of the numerous coal mines located locally back in the late 1800’s. This knowledge also helps determine the plasticity of ball clay located next to coal seams; typically they are more plastic. 
The bottom (thin layer) is free from large particles, and because this is a sedimentary sample; also means it is finer and more plastic. As with all clay sediments; larger particles drop out first, and smaller particles drop out last. Remember, this sample was photographed upside down to capture color variance. So the thin layer on the bottom, is actually the top of the sample. Can you field test plasticity? yes. Make a 1/4 cup of the middle layer, and a 1/4 cup of the bottom layer to start. If you have a scale, you can accurately measure what you add to each sample to create a pliable ball. If no scale; add 1 teaspoon, add a second, and once it begins to form a ball, then add 1/2 teaspoon until it becomes a pliable ball that does not crumble, nor overly wet and sticky. Low plasticity clay requires less water to form a pliable ball, and a high plasticity clay requires more water for the same. Exact? no- but will give you some general sense and direction.
Tom
 

Veering slightly off topic, but I have a special place in my heart for Mack brushes @Hulk. My summertime alter ego is “sign painter,” no one makes a better brush for that. 

Denice wrote "dagger" earlier in the post.
Pinstriping brush styles include "sword" and dagger*.
There are natural hairs and synthetic fibers, many handle variations, profiles, length...
Watching those who can really handle the stripe brush is an education!
fwiw, I use plain masking tape, which makes for a clean/sharp line. Locking the edge down is key - where there's no dust or residue underneath, and the edge is firmly adhered to the substrate. The .7" wide is easy to handle and allows for a wide (sloppy) brush. For curves, I use a better quality/brand masking tape - which cuts cleaner, bends better, and sticks well - and cut strips to the widths I want. The bargain stuff doesn't perform as well, doesn't cut nicely and doesn't bend/curve as well.
It's a preference, and I'll admit it's not just that I've used masking tape for many years in the paint trade, no, I'm also cheap!
That said, I might try the special auto tape one o' these days! I did some taping for a friend's friend who was into auto body - we used 3M half inch tape for all but the curviest parts.
 
*for example, see https://letterheadsignsupply.com/ - there are links for brushes on the main page.

Denice wrote "dagger" earlier in the post.
Pinstriping brush styles include "sword" and dagger*.
There are natural hairs and synthetic fibers, many handle variations, profiles, length...
Watching those who can really handle the stripe brush is an education!
fwiw, I use plain masking tape, which makes for a clean/sharp line. Locking the edge down is key - where there's no dust or residue underneath, and the edge is firmly adhered to the substrate. The .7" wide is easy to handle and allows for a wide (sloppy) brush. For curves, I use a better quality/brand masking tape - which cuts cleaner, bends better, and sticks well - and cut strips to the widths I want. The bargain stuff doesn't perform as well, doesn't cut nicely and doesn't bend/curve as well.
It's a preference, and I'll admit it's not just that I've used masking tape for many years in the paint trade, no, I'm also cheap!
That said, I might try the special auto tape one o' these days! I did some taping for a friend's friend who was into auto body - we used 3M half inch tape for all but the curviest parts.
 
*for example, see https://letterheadsignsupply.com/ - there are links for brushes on the main page.

If anyone is past their 10 article limit, try typing the name of the article directly into your browser. Often you can bypass the paywall on articles that have been made available for promo this way.
It’s interesting to see both the pros and cons of communal studios in the comments section. The upvotes on the assorted comments are revealing too. The person who was complaining about perfume only has 1, after 3 weeks of the article being live. The more positive ones have a LOT more.

Nice article. Nothing like a clay community. I wish that real estate wasn't so expensive where I live otherwise I would start a community studio/coop. 
Betty

continued success with these large platters. Thanks again to all

I haven't taken a vacation since before the pandemic and I'm not up for flying anywhere. What I do is travel by myself or w/a friend, on day trips where there's not tons of people. I may go to the ocean along NH or ME, for a couple of days, off season.
This summer, my primary plan is to use the time to accomplish two things.  One, I will sell an entire room-full of good quality "yard sale" type items. That is actually a lot of work, as it all goes online-not allowed to hold sales where I live.  Two, I will streamline my studio .  There's a good bit of materials, tools, supplies, equipment, the wheel, etc. that I will sell (will just do handbuilding).  I am  freeing up space so I can get back to painting/other media--so that counts as non-ceramics LOL. 

When reviewing clay specs: the alumina content will predict plasticity. The lower the alumina content; the more plastic the clay will be. Example: kaolin is 37% alumina, and nearly non-plastic. Larger grain (micron) ball clays have 27-31% alumina, and typically rated as medium plasticity. Fine particle (sub-micron) ball clays with high plasticity run 24-27% alumina. As alumina levels drop, plasticity increases: bentonite (very high plastiity) has 20% alumina. BentoneMA (even more plastic than bentonite) is highly processed hectorite with less than 2% alumina. Particle size also effects plasticity: fire clays have a percentage of large (20-80) mesh particles that lower plasticity; even though it has lower alumina. High plasticity ball clays are under 1 micron particle size; or sub-micron particles. Example: Kaolin run 2-20 microns typically; which also plays into its non-plastic rating. OM4 ball clay runs 0.67 microns and is medium plasticity. CMC ball clay is just below 0.50 microns and is rated high plasticity. I use Taylor ball clay (not available commercially) that is 0.27 microns and extremely plastic.
When formulating: plasticity ratings matter. For example: a common formulation basis is 25% kaolin, 25% ball clay, 25% silica, and 25% feldspar (cone 10)  25% OM4 ball clay will create workable plasticity. If you changed that 25% to CMC ball clay: the body would absorb water rapidly and collapse quickly on the wheel because CMC is much more plastic than OM4. Let me express this another way: 8% of my Taylor ball clay will produce more plasticity than 25% of OM4. So you have to understand that parameter when formulating. Remember: high plasticity equals high water absorption. Randomly switching ball clays in equal additions (25% OM4 verses 25% CMC) will turn a plastic clay into a “fat” clay quickly. 
Alumina will predict plasticity in most all cases. Exceptions: as mentioned, larger particle sizes will lower plasticity even when alumina is lower. 2. Higher calcium content will increase plasticity when alumina content is higher because calcium creates isomorphic substitution (don’t ask) at a higher rate than sodium or potassium. 
Fireclays have higher inorganic sulfide levels which equate to higher LOI at 1750F. Inorganic sulfides = lignite coal particles.
Tom

Sounds like you’re in a good place to get some clay someone else dug up, cleaned out, and processed for you. I wouldn’t mind that one bit!
Lincoln 60 is a winner in my book. I used it as part of my clay recipe for a few years until shipping costs became prohibitive. (Mine’s very different from yours, cone 03).
My first thought was to suggest blending a local red/common earthenware with Lincoln until you get the mix that vitrifies at cone 6. Tony Hansen suggests it ought to be possible by just adding feldspar (link below).
https://digitalfire.com/material/lincoln+60+fireclay

Hello Hulk! Thanks for the info. The red velvet classic looks pretty close to what I'd try to make if I could find the right ingredients nearby. I've been to IMCO a few times and have used their Great White a fair amount in the past. They are a great company and I have a few friends who get their work fired there. I haven't looked at their dry mixes but that seems like a great idea! For reference, Gladding McBean quoted $118/1000# for both the 60 and 8. Assuming 30% wet to dry that's $118/1300# wet, or $0.09/lb or $2.25/bag, so that's a decent starting target way below most suppliers if it throws and fires good as is. I'll be mixing some up tomorrow and should get a cone 6 oxidation soon and a cone 10 reduction firing in the next month or so.

I read somewhere (can't find the link now of course) that the IMCO 800 clay is actually Lincoln 8 milled to 325 mesh, which is pretty cool too. They also list their Burgundy raw clay as a local CA clay. I wonder where they mine it.. maybe they will tell me if I ask nicely. Anyway, thanks for the response!

I decided a couple of days ago it is time to get started on rejuvenating  our house.   The carpet in the office is worn out and the misc. furniture is old and was old when we bought it  We spent the last two days looking for real wood flooring to match the wood in the rest of the house.   No more carpet,   we think we found it today now all we have to do is get the samples.  The rest of the carpeted areas will get new floor and paint this fall.  I have to shop now for office furniture and a sofa,  our old furniture will be donated.   Denice

Big plan for this summer is to get my partner fit and well and back out doing stuff after 18  months of surgery/partial recovery/surgery/partial recovery/surgery.
I'm going for a week's "summer school" with the Guild of Weavers, Spinners and Dyers - There will be with 300 people spread over 18 different courses.  I will be dyeing with natural dyes.  We will be staying at an agricultural university in Shropshire.
The rest will be filled with hiding from the sun - sun rash is really irriting - in all senses, gardening, spinning, weaving, dyeing and volunteering.  Oh, and some pottery.

Staying home as well, having just wound up prepping our last home for sale, the sale, winnowing the stuff, packing, moving, shopping for a new (to us) home, moving in, unpacking - we're now at home again!
Our son's home is now just ten miles away, much more convenient for ongoing renovations. That will be a big part of non-ceramic plans this Summer.
We just finished "pest work" around and below the chimney - there had been leaking and resultant rot. Now we have a better idea how chimneys should be flashed, also how to shingle, how to install roofing felt...
:|
Next is re-siding the area below, then some framing, drywall and painting to wind up last year's bathrooms remodel, then on to the great room and kitchen remodel...
There are a few projects at our new (to us) home that can't wait very long: refinishing the front door, installing water treatment/filtration, and re-sorting the irrigation system.
Also ongoing, rehabilitation of an injury, and recovery from last week's bout with the dreaded Covid.
Excepting some recent sessions at the wheel, I haven't been in the Studio "doing" ceramics since October last.
I want to have an inventory of green ware ready when the new kiln arrives!
Wiring for the new kiln, adding a circuit for the Studio space (heat pump), sorting the space, installing a wall, door, lighting, shelving ...is all on the docket as well.

A couple of minor points if you are still trying to increase the crazing.

1) Always ink-up (part of) your test-tiles. It can sometimes be hard to see the true extent of the crazing. It also gives you a better idea of the number of cracks which occur after the initial inking.
an example from Digitalfire
 
2) I understand that glaze programs are not too accurate at estimating the absolute COE of a glaze, but  they are quite good at estimating the change to the COE that small change to the recipe/chemistry will make. So maybe you are reaching the point where they might be useful.

See Using Calculation to Fit a Glaze in https://digitalfire.com/article/understanding+thermal+expansion+in+ceramic+glazes

MAGMA and CMC gum have some of the same qualities but they are not the same. 
Good chart here showing the qualities of many glaze suspenders and additives. What the chart doesn't show is how the glaze applies with CMC vs MAGMA when dipped. The latter doesn't  cause the drips/curtaining when used in dipping glazes.

Processing 150 pounds of clay. Should keep me going a little while. I’ll probably do another batch before fall.