I decided to modify the kiln firing schedule for the two large beaver panels- adding another hour to the first segment, slowing it down between a couple of critical temperature points, and then adding a couple of cool-down segments that will slow that down from 1600 to 950 degrees as it passes thru a critical temperature in the 1100 range.
I didn’t add a slow down before now, when the kiln shut off it shut off and cooled, and 2000 degrees cools pretty fast with the power off, so now when it reaches 1600 the heat will turn back on to slow it to 175 degrees drop an hour down to 950 when it shuts off, that will help avoid potential problems from cooling these heavy pieces too fast.
All added up it looks like the estimated time now will go from 24-26 hours to about 32 hours, so if I switch it on at 2pm on Friday it should shut off around 10pm Saturday.
Actually, I think I’ll turn it on to-morrow at 7AM instead
Turned on this morning (Thursday) at 7:10, it’s started it’s inexorable temperature climb from 195º around 6 pm to 2,070º by to-morrow afternoon, so it will be slowly increasing all night into to-morrow. I won’t be able to open it until Saturday late afternoon to see if both beaver panels made it, though as soon as it hits about 1,000º I should be able to at least see the tops of the panels through the upper peep hole, if I can see them through the peephole then they are still standing and didn’t explode, so that will at least be a preview of sorts
Right now @ 272º it’s above the boiling point of water, so the sculptures would be steaming off any moisture, at this stage the programmed segment has a temperature rise of 50º an hour to 300º. It was 80 or 100º previously and all went fine, but I decided to slow it down to be safe even though it adds a couple more hours time.
Looks like the kiln shut down around noon, it was on the cooldown from 2,070º when I checked at 12:30 and it was 2,015º. Now it’s still idling according to the programming I did- until it hits 1,600º and then it will provide enough heat to keep the cooling rate to 175º an hour down to 950º when it shuts off. The first hour it started cooling down it went down 250º, the higher the temperature the faster it’s lost per hour when the heating elements shut off, but that rate per hour falls as the temperature drops.
Probably by the time it’s 1,600º it may naturally only fall 175º/hour or less and not even need the elements turning on, we’ll see.
filled the mold for this with water to see how much it takes, it too just about 2 gallons, so that gives me an idea how much rubber it would take to make a positive cast to turn this design into terra cotta too, it would fit in my kiln easily.
Interesting thing about this piece is, way back around 1978 I was looking for work and not having much luck finding anything, somehow or other I got the idea to look in the yellow pages and one thing led to another I called this place uptown called “Gargoyles” and I remember trying to see if they might take some casts on consignment or something.
One thing led to another and they had me come up to the showroom/factory with one of these, turned out the piece was too big for them to use, but while they couldn’t do anything along those lines they offered me a job instead!
Turned out one of the two plaster casters was leaving in one week- talk about luck!
I was there for about 5 years casting small statues and mirror frame piecs until I had to move out of the city completely.
Still keep in touch with the boss all these years later!
Odd thing was they were at 221 E 21st st in Manhattan, bought a building in Brooklyn about the time I had moved to Brooklyn, and their new address in Brooklyn was 221, 21st st! Meanwhile I moved from 621 Broadway in Manhattan to 621 Bergen St Brooklyn, same number, street name starts with a “B”
KONICA MINOLTA DIGITAL CAMERA
Seeing how the first beaver panel fits in the kiln, cutting it close for height with only 5/16″ between it and the lid but it will work. A second one- red- will go in when it’s drier. I had to stack a couple of shelf supports behind this first one so that if it tends to want to lean backwards it will be stopped by them, the second panel will need the same behind it.
I think next Friday I’ll turn it on. I modified the firing program just a little by adding another hour of pre-heating @195º making it 9 hours so these are good and dry for sure. I also added 5 minutes at the end making it hold at 2,060º for 15 minutes. So overall it will take about 25 hours for the firing process and then “overnight” for cooling down.
What most people know is water boils to steam @ 212º and is gone, but what they don’t know is the chemically bound water in apparently bone dry clay stays in the clay up to at least 700º before it finally burns out.
I could use a larger kiln like the Olympic oval model which would be large enough to lay pieces like these flat, but besides the cost being dramatically higher than this one was, I’d have to upgrade my home power line from the weatherhead on in, the 100amp breaker box and incoming line isn’t enough capacity.
I put the first red one in with this one earlier, and decided to turn the thing on and let it run the first segment @195º until I turned it off now, so they had a good 6-1/2 hours of that amount of heat as an additional tomake sure they are as dry all the way through as they can be so Friday after work I can turn the kiln on and let it go through the whole 24 hour cycle and shut off Saturday afternoon when I’m here.
The first pressed clay is now out of the mold and she came out with a very minimal amount of surface defects that have to be fixed by hand. In the 1890s when these pieces were made the workers pounded the clay in using a small sand bag to ram the clay into the details and eliminate the little “creases” that I seem to get between pieces of clay laid in and pressed next to each other. Might help too if the clay was a little more moist and softer but I hesitate to add water since more water causes more shrinkage. To get a batch custom mixed to add a little more water I’d have to buy I believe a full ton and there’s an extra charge too.
Really want to see this in the red clay but I don’t have enough to do it and only had 50# of this white clay left.
And now 3 days later she is firmed up but not dry, so she can sit like this for about 2-3 weeks to dry before firing.
I decided to take the steps needed to be able to produce this little keystone in kiln fired terra cotta, now after several steps- the final step is pictured, I have the plaster piece-mold to do it once it dries out.
Now I have the very first hand-pressed clay from the new plaster mold out and drying, it took 50# of clay to press the design, and about 10# of that was removed during the final work on it.
Now it will set loosely under plastic to slowly, evenly dry out over the next week to 10 days, it will need to be 100% dry before it can be fired in the kiln. I plan to press a second one either in the same white clay, or the red clay.
The photos show the progression from start to finish, with the back of the sculpture being made exactly the same way the antique original 19th century architectural ornaments were made, not really required for my pieces, but mostly it’s done out of tradition and authenticity.
I also did one in the red clay today;
The first cast in the dirty bronze finish
Now I have this cast finished with the weathered terracotta finish.
The first cast with no finish applied to it yet
Seeing how the lion head fits, the 11″ long backing form looks just right to show that nice classic double curve an inch or so on either side of the lion while keeping the whole thing small and compact .
I have to see if the boxes of clay I have had sitting around are still useable, but once I start making the clay backing form in the template box it all has to be done quickly, including making the complete rubber mold before the clay starts to shrink, including making the plaster support shell since if the clay shrinks the rubber will move with it, so the shell has to be done as soon as the last aplication of rubber is no longer tacky.
Right now I don’t have the molding plaster to make the shell.
Maybe next weekend I can form the clay backer if that clay is ok, and it will firm up a little over a week without shrinking, and then I’ll order what I need in 2-3 weeks and press the lion into the still soft clay and then make the rubber mold.