• Lion blocks

    I fired four of the little hand pressed lions blocks, a cherub plaque and the single section Art Deco in the kiln, and amazingly when I opened the lid, four little shattered lion faces stared up accusingly at me from the bottom shelf of the kiln. I figured at first maybe the vent is cooling the kiln too rapidly but these were not cracks they were blown up under pressure from steam forming inside the clay.

    Despite being dry I thought, and sitting them in front of two box fans set on high for three days they apparantly were not really dry.

    I looked at what makes up the “Slow bisque” profile on the kiln’s electronic controller, to get to cone 04 with this, it has this ramp schedule, in degrees F:

    80 deg /hr to 250
    200 deg/hr to 1000
    100 deg/hr to 1100
    180 deg/hr to 1695
    80 deg/hr to 1945

    I think the 200 deg/hr from 250 deg to 1000 deg is where the problem is going that fast thru that first critical temperature around 550-600 degrees, I’m going to write a program similar to that but change that segment, add in more preheat time @ 200 deg from 2 hours to 5, and run the other four lion blocks I have and see if that fixes the problem.

    On a lighter note, I found the color of the one surviving piece was just perfect, exactly what I wanted, it was right at 2056 deg F or about midway between cone 01 and cone 1, I used a -15 degree offset down from cone 1 which should have made it 2064 degrees but the actual final temperature was 8 degreees cooler than that.

    The Art Deco piece was the sole survivor, the single lion block on the left had his face blown off but it was a clean break and I just glued it back on.

  • Lion block

    These have not been fired in the kiln yet, but I couldn’t resist setting them up for a good photo since the light was so perfect.

  • Odd dream

    I had a really odd dream this morning, what I remember is discovering my office type desk chair rolled very easily on the street in NYC and at first I was with someone else messing around with rolling on our chairs at night, but I soon found a steep street and went down the hill by myself and it was getting very steep and I was picking up speed fast on the chair. Soon I was coasting down at a steady spead about 30 mph and the downward incline continued for miles, I just laid back in the chair, took my shoes off and was enjoying the crusing but quickly remembered I would need to use my feet as brakes to stop so I put my shoes back on.

    After a while the bottom of the incline came and the chair coasted to a stop, so I rolled it along while sitting on it still to a restaurant nearby to find out where the nearest subway was to get home because now I was many miles from home. I went in and I had my arms full of packages and things and as I made my way in the stuff in my arms brushed three new belts off the coatrack and I had carefully put them back up while hoping their owners didn’t notice I dropped them. Someone pointed to the subway and gave confusing  directions I didn’t “get.”

    I went back outside and my chair was missing and I couldn’t find it after looking all over, sad about the loss of the chair I walked down the street to where I thought the subway was but didn’t see it, so I went to  another place nearby  and asked where the subway was and a woman pointed to the corner, but I only saw stairs going down no signs.

    I went down the very narrow stairs that had an arched ceiling and a lot of others going down the stairs, about half way down I struggled with my armload of stuff to get my wallet out and there a $5 bill and two $1 bills, I didn’t know what the fare was but I got the two $1 bills out and thought about putting my wallet in my sock in case of being mugged on the subway, but didn’t.

    A heavy set woman I thought was a subway employee was trying to make her way back up the stairs but me and my armload of packages was a bottleneck she couldn’t get past, I thought she was going to go up to lock the entrance door to close for the night and how lucky it was I arrived to get in when I did.

    I didn’t get to take the ride because that was when I woke up.

     

     

  • Lion block in terracotta

    The mold is finished for this little lion block and the first hand-pressed terracotta is awaiting firming up before I can take it out in a couple of hours.

    The little lion looks like this in the cast-stone version I’ve had for many years as a wall plaque, but now with the addition of the block he originally had, it will make a nice bookend.

     

     

     

     

  • Cherub

    I  gave quite a bit of thought as to how to provision these to mount on the wall and make it simple for clients to do so, unlike the cast stone you can’t embed steel in the clay for a hook, so I came up with a way to slide the heavy wire I use through two attached studs through a premade horizontal hole made in both in the moist clay. The screw slid through shows how it would work, and the hole where the wire is slid through can be filled locking the wire in place since it can’t slide out the other side:

    Meanwhile, I am boiling the first cherub on the stove for two hours to get an absorption percentage based on the ^1 fire of this clay.
    Dry weight is 2.99kg or 6.55 pounds, we’ll see what he is in a couple of hours and whether or not he goes well with salad or potatos when cooked 😉

    Now that the test is completed, the cherub was 2.99kg/6.55# dry
    and then increased to 3.06kg/6.75# after two hours of boiling in a large pot of water, the difference is 0.2

    Absorption Rate
    Once you know a clay body’s maturation temperature, you can test it to find out how much water the mature clay will absorb. Using an unglazed test piece that has been fired to maturity, weigh the pot as accurately as possible with a triple beam scale or sensitive digital scale. Write this number down, then boil the pot in water for two hours. Remove the pot, dry it with a towel, then re-weigh it.

    To find the absorption rate, subtract the saturated weight from the dry weight. Divide the difference by the dry weight. For example, let’s say a pot weighed 0.75 pounds after it was fired to maturity. After boiling, it weighed 0.8 pounds. The difference is 0.05. Dividing 0.05 by 0.75, we get 0.067, or an absorption rate of 6.7%.

    Using that formula I come up with a figure of 0.305 or in otherwords a 3% absorption rate, that’s actually very good since 5 to 6% is where most hard bricks are, so the cherub in this red clay is actually more dense, harder and less absorbant of water than hard bricks typically are and that’s a range where I wanted my sculptures to be so they can exist outdoors.

  • Cherub 295 terracotta

    The hand pressed terracotta sculpture turned out well from the kiln, he is on the right compared to the cast-stone version, clear to see how much the clay shrinks, about one inch

    Now I pressed another one:

     

  • Pressed clay cherub

    Today after drying over the last ten days, and since yesterday in front of a fan on high, I put the cherub in the kiln on the Bartlett “slow bisque” program, but added two hours of preheat time which it will do via a 60 degree F ramp per hour to 200 degrees and then hold it there for two hours before continuing to ^1, which is 2079 degrees, then it has a ten minute hold before shutting off.

    I’m guessing it will be around 6 AM in the morning before it shuts off, and probably it won’t be before 6 PM tomorrow evening before I can remove him from the kiln.

     

     

  • Horse head sculptures

    A simply stunning work of art found at the Charles Luck building, 1111 34th St NW, Washington, DC, the larger version and additional photos of the pair of terracotta horse heads can be found here:

    LINK

    I strongly suspect these original pieces were largely hand sculpted, for the simple reason that they installed only one of these per stable building over the doorway. Obviously  these  types of terracotta pieces were made in a mold, but I am certain the ears were pressed separately in another mold and attached later while both the ears and the head were pliable.
    That would totally eliminate a lot of issues with fragility of the moist clay being removed from the mold, and it would have greatly simplified the mold of the head.

    The head is turned at such an extreme angle that it creates a massive hollow with deep undercuts between the head and the roundel’s concave area, I am betting that either the head was pressed separately from the roundel itself which could have been made with a template on a potter’s wheel in fact, and then joined together later when they were firm enough to handle but still pliable.

    That building in fact where that roundel is, actually has two horse heads on it, and they face in opposite directions, they very well may have been hand sculpted one of a kind models rather than having been pressed in molds.
    I can’t see that they would have gone to the trouble of molds when a building having a pair of these facing different directions was almost unheard of, I’ve never seen it done. It wasn’t like they would have sold 35 of these a year.

    Most of the deep undercuts on these types of sculptures were hand detailed in later during final cleanup after removing from the molds, that also made mold makign much easier and a competant worker would have easily been able to add those few minors undercut details and details as necessary in just a few minutes.
    They were all paid by the piece not by the hour, so you can see how that would have worked out perfectly for the terracotta firms, it wouldn’t have mattered if the worker spent an hour or six on a piece, they still only earned around 25 cents to a dollar per piece.

    Both of these scenarios presents difficulties today in reproducing these works in anything other than pressed terracotta, because with plaster or cement you really for all practical purposes do not enjoy the ability to simply attach separately made parts like this, and with concrete being so heavy and very easy to break it doesn’t lend itself well at all to a piece like this. Plaster is marginally suited to casting something like this in one piece with free standing ears.

    Modern rubber molds usually take care of those deep recesses and undercuts, but if they are severe then they might have to be altered somewhat on the original model to reduce or eliminate them to make mold making and casting practical.

    So it would appear that the only really viable material for this type of a model would be pressed terracotta with the ears being attached separately.

    In the 19th century when these pieces were made, they used water based clay and plaster to make the master original models, I’ve seen pictures, they generally used formed and shaped plaster for parts such as that roundel and then modelled the clay onto that still damp plaster base.

    Once the model was finished and approved by the architect, they made a mold of it while still damp. They did not have the fancy mold rubbers we do today, so they made a plaster piece mold off the damp clay/plaster model and I suppose if they were careful they could pull an additional mold or two off it.

    The original model was then recycled into the clay bin.
    Making the plaster mold off the still moist clay eliminates issues with trying to pull plaster sections off that have undercuts- the model is soft and gives, in the same way my rubber positive casts discussed previously do.
    A big issue with me is that in order for me to do that I’d have to make a mold of my still moist clay model in rubber, make a rubber positive and make a piece mold from that.
    The trouble is, to fill a large bulk of a cavity such as this horse head has with rubber would likely take several gallons, and the material is $200/2 gallon kit. It would take a kit to make the first mold, two kits to make the rubber positive.

    I’ve been thinking the other day about a sort of reverse mold to save materials, that is to say brushing on the Rebound 25 rubber on the inside of the negative Rebound 25 mold, and making the rubber very thick, maybe 1/2″ instead of the usual ~1/4″ and then filling the rest of the cavity with plaster or even self hardening foam attached to the rubber via keying so they stay together permanently.
    Once that is removed like a casting from the negative mold the rubber and plaster “cast” would have rigidity from the plaster mother mold section, and yet, the 1/2″ thick rubber would be soft and have enough “give” that it would easily see plaster piece mold sections removed from normal undercuts on it.
    That would save gallons of expensive rubber not making a large cast completely solid rubber.

    It’s easy to see how this model will require a lot of advanced planning, the finished model would also be limited to my present kiln size 18 x 23

  • Terracotta cherub

    The first matt glazed version of this cherub is out of the kiln, it looks pretty good but I don’t like the gloss on what is supposed to be a matt glaze, I’ll be testing out a few other products I ordered.

     

    KONICA MINOLTA DIGITAL CAMERAThe white crackle glazed version also did not turn out as expected, the jar of glaze which came was so thick it was like wallboard paste, it took 6-8 oz of water just to get it brushable, now I learned it has been discontinued, maybe these results are one reason why:

    KONICA MINOLTA DIGITAL CAMERA

     

  • Terracotta cherub

    The first hand-pressed terracotta cherub, made exactly the same way they made the architectural pieces for building facades in the 1890s has been removed from the mold. The experiment on this is a success, although I need to change a couple of things in the mold making process because there were some issues with the mold making compound I used that caused a very rough pitted surface, that roughness has transferred to the terracotta but that is an easily solved issue.

    The cherub is made from Continental course red clay with grog.

    Here’s how it was done in the old days, hand pressing the clay into plaster molds as these workers are shown doing:

    pressing clay in molds

  • Art Deco bisque

    Now I have the first terracotta from the new mold, it turned out extremely well and I hope to fire it in the kiln this week,

     

  • Terracotta

    Here’s the first terracotta cast fired in my kiln, next to one of the cast-stone casts for size references, it’s clear the clay shrinks dramatically resulting in about a 1″ size loss.

     

    KONICA MINOLTA DIGITAL CAMERA

  • Since I had about a quart of Rebound 25 mold rubber left over I decided to use it to make another rubber positive in a small mold, so after brushing on some of the release on another old Polytek mold I brushed the first application and then poured the rest in the mold. Now 6 hours later it’s cured so I pulled it out and it had cast perfectly with no defects and just as smooth as the original.

    So the surface defects with the Econ 40 were the fault of the Econ 40 not the release or the Polytek mold.
    Think tomorrow I’ll make a plaster piece mold of this Art Deco piece.

     

  • Wolf roundel

    Now that the Roman Ruins panel is essentially finished and needs to dry out slowly, I am ready to cast the wolf roundel st for a client in Brooklyn, NY who  plans to install it in the brick wall of his garage. I had to make a whole new mold of it due to the first mold’s rubber portion tearing far too easily and making it unusable.

    I had put off replacing the mold untill I had an order at hand for it since replacing a mold this size costs around $250 in materials and two days of work. Actually this set has two molds and the second mold should be replaced next.

    Here’s what the complete five piece assembly looks like on the wall in my studio: