I set up my clay model for the mold and the mold rubber along with the plaster and clay I ordered have arrived so I’m all set to do this mold and the plaster mold for the cherub, and set up the grotesque 285 to do it’s plaster mold too. Hopefully in a couple of days I’ll have this new design actually available, and 2 new molds for pressing clay into.
I had to do a little artistic license modification on account of a couple of “layers” in the wings design not quite being far enough out from the backing, so I wound up extending one of the flat ring “gears” up a little further than the original design had.
I also need to overlay another thin run of alternated wing design over the large one as it has that on the original and on what would be a bird’s tail feathers which were represented next to the vertical gears the ribbon winds around. A lot of fine detail yet to finish, some will have to be omitted because it’s just TOO fine and small to do in this smaller scale and with this pretty course clay.
I think I’ll go back to the smoother raku clay for models in the future, it seemed to work a lot better for this.
I started the setup for the cherub to get the original 4″ depth back again.
The new rubber positive has been laid on 4″ thick foam board and the clay built up aound the perimeter. I have it roughed out for now, to-morrow I’ll finish texturing and cleaning up the clay part and I can start pouring the 4 side sections to start with then. There’s virtually no undercuts on the design at all, so the face/front can be done in one large plaster mold section, 5 sections total.
One more section to pour left to go on this- the large “base” that can be done in one piece since there are no undercuts to deal with, and the 4 side sections will all sit on top of the “base” section when I get that done later tonight.
Some more progress for today, there’s a lot of fine detail as well as some interesting textures on the original highway section in the 1970s photo I’m using that is very faint and hard to see that might not translate real well into a reduced scale model of it like this For now I roughed out some of the details in the helmet and below it, and the ribbon below that which winds around the two gears. I had to really study the old photo to figure out what some of the lines were that I could make out and then I realized the lines were a continuation of the ribbon around one gear and up and down and over to the other gear, then the lines made sense.
The ribbon also gets some alternating texture.
And more progress today Sept 3rd
I now have the plaster piece-mold finished for this.
it’s going to be pretty delicate so it will need a lot of gentle care when using it because of all the fine detail, but now I’ll have it to press clay into.
I used up some almost way too soft clay I had left in a bag that was either re-wetted down or some clay scooped out of the back of another sculpture.
I turned the mold over to remove the sections and the bottom section which forms the nose slipped a little and mashed the nose over some, so I’ll have to neater the nose up when I go over the rest of the surface later when the clay is firmer and clean up the details.
After a little straightening up I cast a plaster block the thickness I wanted to get the depth I want for the lion block. The plaster provides a firm solid surface for the clay, is easy to cast square, and since plaster stays damp a long time after it’s cast, it won’t shrink or bother the clay while I work on it. After applying a layer of clay around all four sides I used a metal carpenters’ square as a scraper to get reasonably 90 degree to the face and back- sides.
Doing this also allows for having the clay texture on all the sides with no seam where plaster or other material would meet the clay and have a different texture.
So now he will sit in plastic a little while until I get to refining and cleaning him up a bit as the clay gets a little firmer.
Once that’s done I will be making the silicone mold of the still very moist clay model by next weekend.
This rubber is not terribly expensive as silicone rubber goes, but it is a >platinum< cured compound which should offer a clue on the cost.
It runs about $200 for what they call a “one gallon kit”.
The mold is done and the first cast made and finished for some photos. It took 6 quarts to fill the mold which means when I go to make the mold for clay pressing it will take that much rubber to fill this to make a positive I can take the plaster piece mold off of, might be able to do it with less if I push something in the open back to occupy space to raise the liquid rubber level up to the top.
The photo is of the first cast and with one of my finishes on it. They will make nice bookends too.
I’ll let the little mold dry and see about pressing some clay in it. Meanwhile a pic of the original next to the final expanded rubber version- quite a dramatic size increase from 4-3/4″ to about 6-3/4″
The process wasn’t quite as exact or perfect as the rubber distributor implies, it probably works best on thin plaque shapes.
I had placed it in the bottom of a full 5 gallon pail the last few days hoping the extra water pressure would help force more water into the rubber matrix which is how the expansion takes place- and help straighten the sides but it didn’t seem to expand any further.
The expandable mold rubber is still expanding, now about 6-3/8″ from 4-3/4″ and still going. Hopefully it will level and even out soon once it’s fully saturated all the way to it’s center. I figured it’s 160% expansion
The little expanding rubber lion looks like he has expanded about as much as it’s going to, some distortion evident on the sides but fairly easy to fix along with a few defects, so I’ making a quick and dirty plaster mold of it to press clay into and I’ll use that clay pressing as a model to work on, square up, refine and get a mold off that while it’s still moist and hasn’t shrunk.
I was able to pull the clay pressing out after only an hour, I set it aside under plastic wrap to work on to-morrow and square him up too. I want to get that done quickly so it doesn’t shrink any and I can get a rubber mold off it while the clay is still full sized and moist since the final mold of it will be used to press clay in and when thay dries and shrinks and is fired I want to end up with about 6″x6″ and right now this model is 6-3/4″ x about 6-3/4″
A little more cleanup on her and she can sit around air drying for the next 4 weeks before firing in the kiln
Getting ready to fire my Nr 294 keystone, she weighs 30# dry and has been drying for almost 3 weeks since I pressed her, so I’m going to wait until Friday to turn the kiln on, meanwhile I have her set up in the kiln ready to go.
I can only fit one piece this size in my kiln, another dry panel I have ready to fire won’t fit in with this too.
I have my full shelf on the floor raised off the floor with the 1″ posts, and the sculpture is raised up further on 3 large posts laid horizontally to let the heat/air circulate and to raise the sculpture up a bit higher off the “cooler” bottom of the kiln.
The 3 large posts are set under the 2 side walls and the center of the sculpture which has a web in the center of the upper compartment, so this will give support to these areas to avoid any sagging.
I’d prefer firing this laid on her back as per the first photo, but the kiln is not large enough.
I decided to see if I could get a cone high enough to view through the peephole, and there is one on top of one of the large posts at the bottom, which is actually the top of the sculpture so I can see if that part gets the full heat.
This Continental clay course red with grog and sand will get fired to ^1 which is almost about the edge of where the red starts to turn towards brown.
We’ll see how this turns out next weekend.
I did some more work on the West side highway model. It has plastic behind it and it’s covered with plastic when not being worked on so it keeps the moisture in as much as possible so it doesn’t dry too fast. Even with spritzing it with water and covering it with plastic the clay still dries out, just slower, so the working time window is somewhat short, but as the clay goes from really soft to firming up, various stages in the modelling process can be done.
Roughing out is done first, leaving more clay than needed so it’s mostly removing clay instead of adding on, and then as it get firmer and keeps it’s shape better, finer details can be applied.
I’m almost tempted to made the vertical “bars” in the parapet out of scraps of wood once the clay is dry instead of hand forming every one of them, but then the texture would be different, and the wood strips too square and perfect to match the modelled clay, so it would stand out in not a good way.
I could have made the horizontal pieces out of wood too, but the same issues apply there.
The 2 gallons of Vytaflex came today so I mixed it up and filled th 294 mold with it, the 2 gallons wasn’t quite anough to completely fill the mold, but as long as all the detail is covered it won’t matter as I have to add a 3-1/2″ deep plaster backer to the rubber when it’s cured anyway. Now it will need to sit and cure overnight before it can be removed from the mold.
The rubber positive with it’s new plaster backing block is out of the mold, now the keystone is approximately the same depth the original 1895 sculpture was before I made a shallow mold of her way back around 1980 to eliminate the back that was normally embedded into the brick wall, so the casts could hang ON the wall.
But now with wanting to make her in terracotta she will need the full depth.
I have some final patching and texturing of the plaster to do yet, but I expect I‘ll be working on the plaster piece mold of her this weekend.
The rubber cast is so I can take a plaster mold off this and not have any concernes about it getting locked together by slight undercuts and opposing surface angles, the soft rubber will “give” and the plaster doesn’t adhere to it
The first plaster piece mold section is made for the 294 keystone after I applied a layer of clay to the plaster backer block so I could square the side up and give it some texture. The clay used that way works nicely since the plaster block is still wet so it won’t absorb much water out of the thin layer of applied clay before I poured plaster over it. Now that the plaster section is hard that thin clay under it is no longer needed and it will be scraped off when the plaster mold is done.
3 more sides to do the same treatment with and then a few more sections for the face and base to be done yet too.
I might go and make blocks molds off these plaster pieces so I can make more molds as needed as easily as pouring the plaster rather than having to set up and mold all these sections one by one like I am here.
The block molds would be individual rubber molds of each plaster section, taken off them before this plaster mold gets any wear or damage.
Supposedly plaster molds wear down fairly quickly from the highly abrasive course terracotta being pressed and rammed into them, but in the old days it was of little consequence as almost every building had custom made ornaments on them, so they might only have made 4 or 8 identical keystones for the building anyway- not hundreds of them. More common ornaments like cornices they would have used a lot of and on multiple buildings, so they had to constantly replace the molds of those as they wore out.
I found some time to do a little work on this West Side Highway model. The screw heads are just the right size for the rivets and much easier to use than hand forming every one of them by hand in the clay. The slots in the screws will get filled in before the panel is molded.
I also roughed out the first eagle head a little bit.
I also just ordered another 2 gallon kit of the rubber I need to cast a positive in the new mold for the 294 girl keystone, so next Friday I should be able to cast her, it will take the whole 2 gallons to fill the mold, and then I need to make a form to pour the molding plaster backer block for it, then I can start making the plaster piece mold off that to press the terracotta in.