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CactusPots

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Posts posted by CactusPots

  1. An interesting topic has come up (for me) in the liner glaze thread.  Basically when a glazing or any other procedure is more practical for a production potter or a studio potter or a beginning or casual potter.  A production potters goals are much different from either a studio potter or casual potter.  I'm using the term studio potter to define myself.  Lots of experience, but no interest in making lots of the same pot.  A casual potter simply hasn't made enough pots at all.  For this particular operation, a liner glaze in a mug or bowl with a sharp demarcation to the exterior glaze, the casual potter wants a relatively fool proof method that will give the best chance of success for a good percentage to come out as expected.  No special skills required.  Neither myself or casual potter is going to gear up for a 100 pot run.  If there's a step in the procedure that guards against error, such as getting exterior glaze inside on the liner, it's worth it to both of us to wax the inside first.

    I assume the majority of persons who lurk on this forum are not production potters.  I thought to write my steps for their benefit, as it took me quite a while to figure it out myself.

    It's definitely worthwhile to hear from the pros, I appreciate their input even if I can't always use it.

  2. 3 hours ago, Mark C. said:

    I use my glaze jet to blast the glaze into the upside down pot. If you desire a super strait edge I just hit the top on the power sponger. .No wax no muss no fuss.

    Liam's way is just about as goods well.  Once you have glazed more than 30k times this all can be done almost in your sleep.

    If you glaze the inside of the pot with the blaster and then remove the top, I assume you are putting the not food safe glaze on the lip now?

    The object is liner glaze on the inside (and lip), super clean break and whatever glaze you like (shino, barium, much worse) on the outside.  Not making a production run.

  3. 46 minutes ago, liambesaw said:

    Don't need to wax the line, I do your entire routine there but without the wax.  I do the inside with a liner, then use a large flat knife to knock off any berries and then dip the outside by putting my hand in the mug and dipping it.  Then I wipe the bottom on wet carpet.

    Super fast, super easy, super simple

     

     

     

    Chances are you'll either get a holiday or an overlap.   Unless you've done this 30k times and can now avoid that.  The wax makes it picture perfect right out of the box.  Worth the time, I say.

    The goal is the best possible result with the minimum talent/expertise/experience.

  4. On 1/11/2021 at 5:05 PM, CactusPots said:

    I'm guessing the production potters here don't use liner glazes.  The reason for my thinking is that I don't know a way to make a clean transition between the inside glaze and the outside glaze that isn't just very time consuming.  I'm doing it with latex resist, 1st glaze, wax resist, then second glaze.  It looks good and I don't do kitchen ware very often, so not really a big deal for me.

    I guess the other option would be an overlap on the outside that worked between the 2 glazes.  Not going to happen with a shino or a lot of glazes.

    Here's what I've worked out as the best way to do a food safe liner glaze with completely different exterior glaze.  This is not for the production potters,  too time consuming.  You guys are going to find glaze combinations that don't require something like this.  I'm pretty sure for this effect, this is the best method.

    Glaze the inside the usual way, pour the glaze in, roll it around as you pour it out.

    Holding the pot upside down, get 1/4 to 1/2 inch on the rim.

    When dry, scribe a line down from the rim, all the way through to the clay.  Giffin Grip to the rescue.  Easier to scribe a straight line than brush wax one.

    Using some sort of scraper, remove the glaze below the scribed line.  I like a Xiem tool with a paddle head on one end.

    Using a rabbit ear sponge, clean it up and smooth out the bottom of the new glaze line.

    Wax inside and rim.  Much easier to wax a raised glaze edge.

    Holding the pot from the inside, glaze the outside bottom first right to the wax line.

  5. 46 minutes ago, Babs said:

    For those who doubt the learned folk, try it yourselves because as always it depends....and logic is for those with ope eyes and ears.

    Re compression of bottoms, making bowls using length of pipe to flatten clay, didn't do the out to in on a couple, but lots of compression  overall, S cracks on the ones without the out to in action...could have neen Murphy though

    I've learned a lot from the posts on this forum.  I do think though,  that never more than today, "how do you know this?" is always an appropriate question.

  6. 9 hours ago, Dick White said:

    I have access to both Bailey and other rollers. Based on what I know about the properties of clay, I believe the single pass capability of the big Bailey rollers is inappropriate advertising. Clay, when rolled into slabs tends to shrink more in the direction that it had been rolled. A slab rolled in a single direction, whether in a single massive crunch through a Bailey big boy or multiple rolls by hand with a kitchen rolling pin (all in the same direction, contrary to conventional practice of rolling in different directions) will shrink back more in that dimension. Thus, a perfect circle cut from a unidirectional slab will dry to an oval. Perfectly fitted pieces will dry together uniformly only if assembled when the direction of the roll is maintained across all the pieces. All that said, I love and prefer the Bailey big boys, but I never roll in a single pass. Set the roller for a thick slab, flip it and rotate it for a second pass with the roller set thinner, and maybe a third time to the final thickness.

    Have you ever actually tried this as an experiment in practice or are you only talking theory?  I'm not disputing what you are saying, just asking if you've ever set up a trial and measured results.

  7. 9 hours ago, Sorcery said:

    I almost bought Advancers but they talked me out of them for my electric conversion gas kiln, due to a possibility of shelf post sandwiches retaining heat, while the rest of the shelf cools, which can lead to cracks.

    I reckon if your burners are close to the bottom shelves, you may find it impossible to heat a shelf evenly slow enough.

    If it ain't broke...eh..

    I would change knowing I may have a couple crappy firings with the new setup.

    Sorce

     

    I have a cut shelf for my damper.  It has to be ridiculously uneven as the inside is getting direct blast and the outside 6-10 inches is exposed.   Not the advancers, but the cheaper silicon carbide shelves.  Have not seen a problem with this setup.  I have a dozen or so firings on the only set of advancers that I have and I only use them on the top where the cooling is slowest.  They are still perfect.

    So here's another question:  are the advancers more sensitive to thermal differences than the standard silicon carbide?  Except for the fact the SC shelves warp, they are just as good for glazes not sticking as the advancers.  Yeah, the advancers are lighter also, but the warping is the big factor.

    I've heard that "if it aint broke" thing before, but it doesn't apply to me.  I'm a diagnosed tweaker.  Not the druggie kind.

  8. I've been operating my home designed and built 36 cf ceramic fiber downdraft for 20+ years under the premise that extra mass at the lower part of the kiln would make the kiln fire better.  Primarily, I'm talking furniture.  I have 1 inch mullite shelves on half inch posts over the kiln floor (2x k26 soft bricks) and then one set of 4 18x18 3/4 " shelves.  The rest of the shelves are silicon carbide and advancer.

    What I'm thinking about is how necessary are the heavy shelves low in the kiln?  Frankly, I'm tired of messing with kiln wash and would like to add 2 more sets of advancers.  I guess the only way to know for sure is to try it, but theoretically speaking what do you think?  

  9. It's definitely easier to finesse too soft clay than try to work (throw) with slightly too hard clay.  Harder clay will let you more easily be aggressive with expanding, etc, but not really worth the pain.  There are several good techniques for making commercial clay softer that are worthwhile.

  10. I'm not that good at throwing even after 25 years, so I use this cheat.  Using 2 ribs instead of your fingers will  even out the clay.  This is really nice as the final touch to remove throwing marks.  Assuming of course that you don't want them.  Sometimes I do this with another standard pull following, especially if I've left too much clay at the bottom.

    I use the next smallest Sherril blue ones for this.

  11. New clay bag---> collect clay scaps and slag---> pug and age clay---> throw away.  I usually cut the clay bag to take the really wet clay out for the pug mill, so it's done at that point.  Pretty good to get three uses out of one original.  I'm at least 30 bags ahead at this point, so that's good.

  12. On 1/9/2021 at 8:23 AM, CactusPots said:

    Shop vac takes care of the dust.  Or a big ass fan outside.

    I did build "flaps" initially when I built the kiln.  It was a tin box, maybe 6" x 6" filled with ceramic fiber,  The bottom one is still in service, but the top one burned out a while ago.  Hence the plug.

    Once again, I make a comment thinking gas kiln and everyone else is talking electric kiln.  How anachronistic I am.

  13. 7 hours ago, Mark C. said:

    I use liner glazes nearly every week.

    I'm a production potter

    We use a glaze jet on most all interiors (you can look up this homemade tool) It sprays a glaze straight up.  It fits into any 5 gallon bucket. Its a production tool. I did a how to in studio potter long ago on how to make this tool. On about 1/3 of wares like glasses and 1/2 glazes and certain mug extrior colors I use white interior glaze. on the rest its a rutile blue-booth clean very well and are tough glazes. They play well with  all my glazes as well. Since you have the pot inverted upside down the lip edge is a clean perfect glaze job and if its not a large wet sponge laying on counter makes it so with a Quik twist on the lip.

    But does that get you a dead sharp line between the glazes?  Or does the "play well" part mean the overlap looks ok?

  14. 8 hours ago, Hulk said:

    Functional ware is liner glazed by definition (imo).

    2 disagreements with this statement. 

    First, the reference to "functional ware".  Kitchenware or food ware would be more accurate as (for instance) my planters are as functional as your bowls and mugs. 

    Second,  (imo) when potters use the term "liner glazed", they're assuming a different glaze on the outside that is not intended to contact food.  If you glazed the entire piece with a standard food safe glaze, you wouldn't refer to it as a liner glaze.  The intent of the exercise is to use a wider range of glazes than would be allowable with a single application approach.

    The first one actually bugs me since potters making planters seem to be held in lower esteem (imo).

  15. I'm guessing the production potters here don't use liner glazes.  The reason for my thinking is that I don't know a way to make a clean transition between the inside glaze and the outside glaze that isn't just very time consuming.  I'm doing it with latex resist, 1st glaze, wax resist, then second glaze.  It looks good and I don't do kitchen ware very often, so not really a big deal for me.

    I guess the other option would be an overlap on the outside that worked between the 2 glazes.  Not going to happen with a shino or a lot of glazes.

  16. 2 minutes ago, Min said:

    Kiln bricks to carve out plugs make really good plugs but it's dusty if you use power tools, I've found whittling them by hand isn't as dusty but still needs to be done outside (wearing a respirator).

    Other option would be to use peep "flaps" instead, 2 of my kilns use these. On the Euclids kiln they are made from an open groggy clay, on the ConeArt they are stainless steel. Would need to add 2 self-tapping screws for each. One screw to attach and pivot the other screw to hold it in the open position. Advantage to using flaps instead of plugs is they don't get dropped or lost. Disadvantage is they do get hot so can't touch them with bare hands but easy to flip them over with a scrap of brick or a post (or wear gloves).

    edit: let me know if you want pictures and I'll take some closeups. 

    Shop vac takes care of the dust.  Or a big ass fan outside.

    I did build "flaps" initially when I built the kiln.  It was a tin box, maybe 6" x 6" filled with ceramic fiber,  The bottom one is still in service, but the top one burned out a while ago.  Hence the plug.

  17. 1 minute ago, Bill Kielb said:

    According to the features published it can automatically and also has a speed control.

    Pretty sure mine doesn't.   Just start, stop, pug and vacuum on the control.   I can see where it would be useful.  Maybe the doc you're looking at is a new upgrade model.

  18. I used Peter King clay.  Not the easiest to throw, but they have held up well so far (maybe 60 cone 10 firings).  You could maybe just use Soldate 30 or add a bunch of grog to a basic cone 10 white or light colored clay.  I think if I was to do it again, I'd extrude the spy holes square and fit a square tapered soft brick plug.

    Making a mold form for castable would be tricky.  I don't think it would be durable unless it was pretty thick.  I used castable cement for my exhaust damper box.  At least one piece cracked, but is still functionable.

  19. On 1/6/2021 at 6:57 PM, Bill Kielb said:

    Slower speed, better mixing, less bypass, likely more uniform moisture content. Wonder if he even has to mix longer. Hmm, might be a cool lesson here as aging would tend to even out the moisture content as well. Maybe we really don’t need to hope for foul smelling clay?  Maybe I can take that warning sign down that says no bad mold spores allowed! Just some food for thought.

    What kind of pugmill has speed adjustment?

  20. 25 minutes ago, Min said:

    Interesting thoughts here. To rule in or out the microbes or vacuum theory I'ld try taking the scrap, misting it lightly with water then hand wedge it and see how plastic it is. If it's plastic then it would point to the vacuum being the issue. I can't see how the microbes would decrease in the pugger unless it was being pugged for so long that the clay gets hot enough to kill off the microbes. Doubt it would get hot enough though.

    Or taking a fresh bag of clay and running it through the pugmill.  I've not tried this, but I suspect if it was hand building firm and not throwing soft, it would come out short(er).

    The process SBSOSO is talking about dries the clay significantly by the time it gets back into the pugmill.  It's an interesting question why they were able to get away with immediate use after pugging scrap and now they can't. 

    Lots of ins, lots of outs and lots of what have yous.

  21. I noticed the exact same problem with my reclaim clay.  I called Laguna and asked their clay "expert" about it.  Their reply was that the commercial pug mill they use has so much more powerful vacuum that my Peter Pugger.  I don't know if I fully buy their explanation, but I don't have a better one.  The working solution I'm using is to pug wet and age.  Very nice clay that way.   I think Sorce may be on to it.  By the time I get around to a session with the pug mill, the scrap has been sitting in bags wet for quite a while.  Sometimes even a touch of green.  It's definitely not short coming out of the pugmill now, but it's really soft and needs to age to be ready to use.

  22. On 12/28/2020 at 1:29 PM, Min said:

    Just an idea but if you know the size of the finished slab (roughly) and you know the size of a bag of clay you could do the math and go by the volume of slab and clay bag. Laguna box of clay is 12X12X6 so one bag is approx 12X6X6 which has a volume of 430 cubic inches. Your 30X30X0.25" slab has a volume of 225 cubic inches. Since the bags of clay aren't quite as big as the box and to make the math easier I'm rounding the bag of clay down to 400 cubic inches.  225/400 rounds down to 9/16th of a bag of clay, or just over 1/2 a bag. 

     

    I think this is the right approach.  I don't know where the math failure is here, but half a bag of clay will not give you a 30x30x 1/4" slab,  just from experience  estimate.  I don't know why Min's calculation is off.  The pug is a little smaller than  12x6x6 to actually measure it,   Not by that much (half). The rough calculation of 432 cubic inches by 25 pounds is  0.05 lbs per cubic inch. 

    I rolled out a 1/4" slab and cut it to 12"x 12" and it weighed 4 lbs almost exactly.  That comes out to 0.11 lbs per cubic inch.  This seems to work for my calculation and gives me a better way to estimate what I need. 

    30x30x .25= 225 x .11= 24.75  A whole bag.

     

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