baetheus

You can use wooden dowels as supports and leave them in during the bisque (or even during glaze if you single fire). It's best to alter your firing schedule to climb more slowly through the organic burn out section (500F to 700F https://digitalfire.com/temperature/36), about 100-150F/hr if you can manage. Some sculptor who makes a lot of dogs uses this method. He also will block out the rough shape of the sculpture using entire 25lb blocks of clay, sculpt away until most of the work is done, blast the surface with fire, cut away a few lids and hollow out the sculpture, and then score slip his "lids" back on. I watched a video and he was incredibly quick using these techniques. Don't remember his name though, sorry. Hope this helps!

You could buy a 50lb bag of grog (about $35 from my local supplier) and wedge grog into your bmix, best of both worlds really. I'd start with 30-48 grit grog and keep your additions of grog under 7% (I use 4-5% but am not careful with measuring) by weight (ie. if you wedge up 500 grams of clay don't add more than 35 grams of grog). I sprinkle the grog onto my wedging surface and then wedge right on top of it until it's well incorporated, about 50 turns if you spiral wedge. Hope this helps!

In addition to wiping you can also spot saturate with some water by either pre-dipping in water or dabbing with a soaked shaped sponge. I teach it to my students when they don't want to wax the bottoms of their pots. 1. Apply water to areas of pot you want to be less glazed. 2. Apply glaze as normal. 3. Give a little shake, blow on the less glazed spots, or dab with a sponge.

@Bill Kielb Thanks for the response. 60-80 grit for big drips and 180+ for finishing bottoms sounds about right. It's really unfortunate that my favorite results tended to be the glazes that got the most movement, but at least it was a mostly successful experiment! As for my dips they are pretty quick in general, definitely 3 seconds or less if I'm going to layer. I didn't mix these particular glazes (they are older recipes from the craft center that I tech at) and they don't have any gravity documentation. It's mostly a go by feel studio so my mileage with technique is going to be varied for the next month unless I take over some of the glaze mixing : /. I'll be honest, I seriously considered trading in this dark groggy clay for a white grogless stoneware because of all the struggle it imparts on making work (best thrown soft, but don't use a lot of throwing water, if you trim you gotta burnish, if your walls aren't just right you'll get some bloat, all your standard glazes get an iron oxide shower, half the glazes wanna crawl, rough bottoms, many people don't like texture, etc etc etc). But after a few days I'm back to looking for solutions! Anyway, thanks again for the response.

Hello All, I have a few questions about finishing glaze fired work. In general, I try to do as much finishing at the greenware stage or on the wheel. For my mugs this means: 1. While throwing I compress the base to about 3-4mm thick, wire off with a curly wire to get the final texture, and clean the bottom curve with a wood knife. 2. I use very little water, preferring to use slip from the previous mug while throwing. 3. I finish the rims of the mugs with slippery (covered in slip) shammy leather, mostly smoothing and shaping. 4. While the pots are on the soft side of leatherhard I round off the bottom corners with my thumbs then gently tap in a little dome in the bottom. However, I have been using Laguna's Death Valley clay https://www.lagunaclay.com/product-page/wc835-death-valley-red which is decently grogged and I've had some feedback that the rims are too rough for some people. Here is a picture of the rims (Personally, I don't mind the roughness and can't feel when drinking from these mugs). Thus my question: Is there some way during making to reduce the roughness I'm getting in my rim or to smooth it after glaze firing? My other questions are about dealing with glazes that I let get away from me. In my last firing I tried about 50 new glaze combinations and 10 of them came out beautiful but ran onto the shelves. Some drips are quite small: and some are quite large: Before now I've primarily been testing single dips of single glazes to keep it simple, and thus haven't run into dripping. I was thinking about picking up one of these diamond sanding discs (https://www.clay-king.com/pottery_tools/diamondcore-tools.html) to clean up what I can, but was wondering if you all had advice for the following: 1. What grit diamond pads would I use for glaze cleanup and polishing to save these pots? 2. How much glaze dripping is possible to correct or worth correcting? Thanks in advance for any advice you can give me and I hope you are all having a wonderful weekend!

I hope this is an okay place to post this, if not please let me know. Hello All, My studio setup is a bit stymied right now so I'm looking to fill some time between October and November with a road trip around the western United States. I'm looking to visit potters and studios as much as possible! If you are open to a visit to talk pots or receive some free grunt labor (I have professional skills with software engineering, intermediate skills building/fixing/maintaining pottery equipment, and am not above helping wedge, reclaim, or make clay and glazes). Currently I plan to stop by Archie Bray, Cobb Mountain, and Cider Creek Pottery. If you have recommendations for any other programs or places that I can reach out to please let me know. Take Care, Brandon Blaylock

Hiya, since you are asking for information at the junction of practicality and aesthetics I might suggest trying to write on flat surfaces. For me it's not *hard* but it's not easy either. As something to think about you could consider shaping your pot a bit while it's leather hard. Here is a video of Lisa Hammond teaching how to make her squared off bottle, which requires tapping and shaping the pot to have "flat" sides: I only point you to this since I prefer writing (and reading) on flatter surfaces. Hope this helps and I'm excited to here how it goes!

@Kelly in AK I do feel very lucky, and not just with clay! Almost all of my equipment was free or cheap! Free kick wheel, free clay mixer, free wareshelving, an old skutt KM1227 for $1000 with furniture, free space in our shared garage, etc etc. Most of it needed a lot of love but ultimately it was much cheaper than buying new/used. I've made a few trips now to IMCO to talk clays and ingredients and they've been very generous with their time and information about material sources and compositions (even compositions of their "proprietary" clay mixes). @PeterH I did read about anhydrous borax and ended up on several welding and knife making forums! Turns out borax can be used for surface prep in those fields. There was questionable information about cooking borax decahydrate into your own anhydrous borax but that would be a last resort for me. I'm not yet interested in making my own frits :D. That said, there is a little hope on the Borax Decahydrate page on digitalfire. It seems that the granular borax (which is what my source is) might not be very soluble. Either way, I've got 50lbs of it and I intend to find out what's what. @Callie Beller Diesel Interestingly, I've share a few emails with John Britt with questions on information (or, as you say, concise information) from his midfire book. He's been quite patient with me but I don't really want to push it. Besides, I think I'm a little bit outside the standard glaze path and that necessitates testing on my end anyway. That said, good to know table sugar will probably work. I was headed in that direction already :). I'm glad I decided to sign up here, you've all been incredibly welcoming and helpful! @akilpots You're spot on. Originally, I had pulled the 4% zinc oxide in the recipe you likely read from Val Cushing's Transparent 3. I read all about Zinc and it's interesting effects on color changes when used with coloring oxides and didn't really want to use it. I've since been on a Borax kick, which is in the direction of the advice you've given if not exactly the standard choice. Thanks for your reply! @Kelly in AK and @Callie Beller Diesel I've attached a photo of my space in it's almost finished state. Callie, the rolling stand for my mixer brings it to where I barely have to bend over to reach the bottom of the mixing bar, and my clay bins with the red stripes on the left are even with the top of the mixer so I'm not breaking my back scooping out clay. Also, you can see that aside from a little space to the left of the window there isn't much room for buckets of glaze to hang out without perpetually being in the way.. I've been thinking on building another rollie cart for buckets but I'm going to wait until I experience that problem before I put together a solution. Kelly, aside from the bench on the left everything else was pretty much donated by friends and strangers alike. I am extremely lucky and it's helped me want to keep working hard. I'll be waiting a week after I hydrate those clay tests before I roll them into shab bars and test cups so I expect to have an update for you all in 1.5 to 2 weeks. Thanks again for all the awesome feedback.

@Callie Beller Diesel Hey, thanks for the response! I must apologize because I've made a ton of changes to the glaze recipes I've been mucking with on Glazy. At one point I had somewhere around 30 different iterations that I was basing on various books, other glazes, and conversations with local potters. I realized that I wouldn't be able to test any of them until I nailed down the clay body so I deleted all but one of them. The one I kept (and that you probably looked at) is not fully cooked! It is a quick copy of a cone 6 clear from here: https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2753&context=theses that I dropped the bentonite from and subbed wollastonite for whiting/silica, and upped the kaolin to bring it out of the crazing zone on the stull chart. I'm really appreciative that you even looked at it! That R2O:RO ratio isn't mine though, and whenever I pull in a glaze and keep the "chemistry" while modifying ingredients I feel like I'm butting against my own serious lack of knowledge about materials. Ah, yeah, borax.. I suppose the ultimate reason for me wanting to start with borax is that it sounds exciting! I'm a fresh potato when it comes to glaze formulation and mixing and using borax will force me to practice since I'll only be mixing up as much glaze as I think I'll use in each glazing session and won't be keeping it around. For me personally this kind of thing is invaluable, right up there with using a kick wheel and making my own clay. It leads to all kinds of unexpected outcomes. It also helps that I have around 85sqft of studio space so keeping buckets of glaze around is almost a non-starter. However, you are right that I focus perhaps a bit too much on optimizing costs, I definitely have the spreadsheets to prove it. So far making my own clay is a substantial increase in my hourly pay. For mugs alone it's a $14/hr pay increase. The best I've been able to get out of my glaze cost calculations is about $1/hr and that's within a margin of error, but I don't mind playing the numbers game while I wait on the electrician. As for an actual glaze recipe I don't have one yet! But in general I 100% agree with everything you've outlined. When playing with glaze calculations I have been targeting 0.22:0.78 R2O:RO ratio, 7.5-9.5 Si:Al ratio with Al around 0.35, and 0.13-0.17 B2O3 as the primary flux. I've probably put together two dozen recipes that are in this ballpark but until I can get my clay body dialed in it's all been theory work. It is good to know about sucrose helping with wollastonite agglomeration, I'm sure I'll run into all kinds of problems like this as it's in my plan to raw glaze and single fire, both of which offer their own sets of chemistry and material complications. However, I am moving towards some real data. I mixed up a biaxial test of clays today and should have time to hydrate them this week.

@glazenerd Sorry for the late reply. Thank you for this information. I'm still waiting on an electrician, the city of Davis, and our electrical company to sort out whether I actually have the necessary 48Amps available to drive my kiln before they run the copper. Lots of fun, that is. Anyway, I've come back around to thinking through clay recipes and I am hoping that you'll offer more wisdom. Unfortunately, I'm reliant on someone else to fire my test bars right now so I don't have any solid data to interpret yet, thus everything below is theoretical. To make things easier, I've put the final versions of my chicken scratch notes for clay and glaze starting points on glazy.org here: https://glazy.org/u/baetheus/recipes First, let's start with clays. https://glazy.org/recipes/358868 and https://glazy.org/recipes/358852 1. Based on this part of your comment, "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." I started looking at wollastonite as an ingredient for my clay body instead of straight sil-co-sil. According to Tom over at digitalfire the physical properties of wollastonite reduce shrinkage and from your comment the calcium could potentially aid in plasticity (although I sense potential nuance here). 2. When mixing up test batches of lincoln 60 and lincoln 8 I found the fresh mixed (+30% water across all blends was sufficient) wet clay to be fairly plastic but not immediately throwable. I did not age any of the blends yet, but I am confident that I will need to increase plasticity--thus the addition of 2% bentonite as a start. 3. Using your basic notes of 75% Clay, 15% Feldspar, 10% Silica as a starting point I adjusted ingredients, keeping total clay below 75%, until glazy listed the Si:Al ratio as somewhere around 5:1. Does this seem sensible? Second, your namesake, glazes. Originally, I had planned to start my glaze journey by simply using the "cheapest" clear glaze recipe I could find in the John Britt midfire glaze book. This looked like it was going to be the Val Cushing Transparent 3 glaze. However, after spending the entire morning reading about the end of Gerstley/Gellespie Borate and then finding the physical sources of all of the other ingredients in the clear glaze table of Britt's book, I decided that it might be better to formulate my base glaze in the same spirit as my first clay body. This is to say, start from scratch with the same constraints. To this end I used the Val Cushing Transparent 3 glaze as a starting point. https://glazy.org/materials/1577. I have two starting points, one using Kaolin from a mine here in Ione, CA and another using the Lincoln 60 or Lincoln 8 clays. With the exception of silica added to the glaze using kaolin, my approach to both formulations was that same. Again, please correct me where my approach is incorrect. 1. I started with a similar amount of feldspar, choosing minspar only because of the drift I've read about in custer feldspar. After reading through digital fire I convinced myself that the feldspars (neph sye, custer, minspar) could not work as the only melters in a glaze, since they don't melt on their own at cone 6. 2. From there I added 10% kaolin to suspend the glaze. 3. Then I added 1% zinc oxide as a primary flux instead of one of the borates. Although gellespie borate comes in at less than half the cost of zinc oxide, it requires 13x as much material than this formulation. My hope is that 1% zinc is enough. My concern here is that it's likely my first colorants will be the iron oxides, which I've read are dulled by zinc oxide. I'm also concerned that 1% will not be enough to achieve a full melt. 4. Lastly, I shored up the glaze with wollastonite and silica, believing that the calcium would strengthen the glaze and using the silica to push the Si:Al ratio as close to Val Cushings 8.2 as I could. From there I pretty much played with materials until the UMF formula was as close to the V.C. Transparent 3 glaze as I could get it. In conclusion, I hope that this all makes sense and any input you'd have on how I might change my planning process would be greatly appreciated. Additionally, if you have any advice for which materials to start with as far as line blends are concerned that would really help! P.S. I didn't mean to single out glazenerd here. I would love to hear thoughts from everyone on any of this process. So please, help me learn!

Woo! This looks like a good amount to start with. Thank you all for your replies! I will answer them each below. @Kelly in AK I've heard from a few people that Lincoln 60 and Lincoln 8 are pretty solid as a starter for a formulation so I'm glad to hear a bit of an echo for that from you. I picked up some Nepheline Syenite, Bentonite, and grogs at 100 and 200 from IMCO today and am starting with bars and cups at cone 6 oxidation next week as well as melt tests for the non-grogs. The Digitalfire site is new to me, but I'm a little concerned about the drastic mismatch between their chemical composition and the sheet I have. Either way, I'll be finding out what's what. There is also a question of how drasticly different the recent extractions are from historic Lincoln clays. @glazenerd If I'm reading this correctly alumina and particle size are the primary indicators of plasticity. This is important because plasticity is an indicator of water absorption, which in turn affects how well the clay throws (strength under deformation), how it dries (shrinkage), and likely other properties (how it takes to raw glazing when leatherhard or bone dry). In my specific case I am beginning with two clays with 24% and 24.5% alumina (or 29% and 32.5% according to Tom Hansen). If I'm to start with the simple test of adding nepheline syenite a270 into each clay starting at 5%, my instinct is that plasticity should increase. This is because wikipedia lists the alumina content of nepheline syenite at 20.96% and a270 indicates a somewhat fine particle size. In the case that the clay bodies I have are closer to Tom Hansens numbers this should be fine, since the higher alumina there indicate medium plasticity, and I might need to add in 1-2% bentonite to achieve a "fatness" that feels good to me. In the case that the sheets from Gladding McBean are correct then I expect that the body will be much too plastic, and I suppose I'll look into sourcing a kaolin from ione mineral company to compensate. Am I moving in the right direction here? @Callie Beller Diesel I agree with the backbreaking work, taking apart the soldner was its own adventure in strength vs ingenuity. I have the whole mixer up about 11" total on a platform with fat casters so I can scoop out the peels without stooping at all. I also plan to make my rolling clay bins taller but not deeper for this same reason. Hoping my body thanks me for it, since I'm also subjecting it to an old lockerbie kick wheel. The reason for my choosing the lincoln clays as a starting point is that they are dirt cheap and only a 45 minute drive away. I did some napkin math yesterday and it's looking like I can keep this clay down around $0.12/lb including additional materials. To me this is the difference between breaking even at 140 mugs sold a month and 230 for the cheapest dry commercial blends in my area, so it's at least worth exploring the option. This digitalfire site is awesome! I wish I had joined this forum earlier and found out about it! Thanks for the link. @neilestrick "One thing to thing about is where you really want to spend your time as a potter- making clay or making pots." If I'm being honest, I want to do it all. If I were ten years younger starting out I would likely be hunting clay veins on blm land to stake claim, and I still might do so in a year or two. For me making the pot starts well before the wheel. That said, it's entirely possible that I'll get six months into making my own clay and decide to bail out of it. I don't think that'll happen but if it does you can be sure I'll be taking your advice. As far as the easy clay to start with, the truth is that the Lincoln mine gifted me a good amount of dry material and I'm simply excited to see what I can do with it. @Min I agree, that and the big difference between my spec sheets and Tom Hansen's numbers (and glazy's https://glazy.org/materials/15480) made me leery at first. However, after reading all of this good advice, digging into digitalfire, and coming up with a plan for either case, I'm more excited than concerned. Again, thank you all for your replies. If anyone is interested I'll post up my first test plan and the results when I have them.

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!

Also, general/practical (read: not included in academic books) information about formulating and testing clay bodies would be useful for me, as I'm still very new and inexperienced. I'm sure some of the tests are common sense. I could see testing absorption being something like weighing a fired piece, soaking it in water, and weighing it again. And since I'll be starting with a clear base glaze for this body I believe any glaze fit issues will be glaringly visual. I'm sure there are other methods and techniques that you've all developed or learned that aren't in the literature I have access to and I'd love to learn them too! In short, I am in your care.

Hello All, My name is Brandon and I'm starting a studio pottery in Davis, CA. I've collected a good amount of old and often broken equipment that I've repaired, the latest of which is a Soldner Studio mixer. In honor of this equipment I've decided to start making my own clay from local sources (Exciting for me!). To that end I visited Donny over at the Gladding McBean pit in Lincoln, CA today and he gave me spec sheets as well as a bit of their Lincoln 60 and Lincoln 8 clays. Now I'd like to turn these raw clays into something useful for throwing and firing in oxidation at cone 6, but my normal resource for these things (Clay and Glazes for the Potter) is rather slim and advises experimentation but nothing really specific as far as clay composition is concerned. Of course I'll be experimenting, but it's nice to have a starting point! It's also nice to have a clear goal. Mine is: * A good plastic throwing body for functional ware. * Capable of being slipped, raw glazed, and single fired to cone 6. * Final absorption of 2%-. Here are some of the things I think I know: Lincoln 60 Fireclay Technical Data (Dated 07/09/02): Silicon Dioxide: 54.31% Aluminum Oxide: 24.49% Ferric Oxide: 1.92% Calcium Oxide: (Less than detection limit) Magnesium Oxide: 0.06% Sodium Oxide: 0.33% Potassium Oxide: 2.02% Titanium Dioxide: 2.23% Manganese Dioxide: 0.006% LOI @ 1750F: 9.50% Moisture @ 105C: 2.48% (Assuming this means chemical water) Undetermined: 2.65% Lincoln 8 Fireclay Technical Data (Dated 07/09/02): Silicon Dioxide: 55.91% Aluminum Oxide: 23.92% Ferric Oxide: 4.00% Calcium Oxide: (Less than detection limit) Magnesium Oxide: 0.06% Sodium Oxide: 0.34% Potassium Oxide: 1.96% Titanium Dioxide: 1.90% Manganese Dioxide: 0.012% LOI @ 1750F: 9.10% Moisture @ 105C: 2.21% (Assuming this means chemical water) Undetermined: 0.59% Where possible, I'd like to use only local clays. If I need it there is a company mining Kaolin down in Ione, CA that I can potentially get Kaolin from if they ever return my calls. I haven't found a local ball clay, and I think I might need one if I'm to raw glaze, but that's a problem for future me :D. Anyway, thank you for reading this far and I look forward to the wealth of knowledge this community has to offer!