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Jeff Longtin

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    Mold making, slip casting, porcelain,

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  1. Good Morning Anna. Welcome to the Forum. Not really able to give you the answers you're looking for. Mixing your own would be the best way to adjust your recipe. I'm curious about an object that requires a 38 part mold. (Pictures?) As is, you're looking to change the clay to accommodate the mold, have you thought about the opposite, change the mold to accommodate the clay? (That's where I would start. Most production molds are in the 2 - 4 parts range. ) As you don't know the composition of the clays have you tried simply mixing them together? My guess is that any adjustment, to the Bone China clay, will result in reduced translucency, is that acceptable to you? Most Bone China objects I've seen were not made with complex molds but instead were made with several simple molds and many pieces were then assembled to make a complex form. Is that an option in your situation? Good luck
  2. Min - Rather than use roof flashing I use thin plastic sheeting. (I was working at a large corporation, years ago, and they were transiting away from thin plastic sheets, to protect desk tops, to a formica desk top, so I collected lots of thin plastic sheets.) While the plastic sheets are nice, when I mold round forms, (as opposed to a square pouring box) I sometimes forget that they need to be held down, at the bottom of the shape, as well as strapped together, at the top of the shape, to prevent the whole thing lifting up. (and covering my shoes and pants with a thin layer of plaster splatter.)
  3. Hello Hyn Patty, Does this bring back memories??? I was introduced to Seeley's back in the 90's when I made a mold for a local "ceramics" shop. (I was also introduced to Bell Porcelain.) Coming from a "potters" background, (i.e. Minnesota Clay #2 Stoneware.) Seeley's and Bell were something of an eye opening experience. It was the first time I had a chance to cast BEAUTIFUL porcelain objects. The ceramics shop that hired me to make a few molds was very active in the doll making universe. Both Seeley's and Bell were popular among the doll making crowd. I found Seeley's to be more workable but more of an "ivory white" color. I found Bell to be a true "bone china" appearance but much more difficult to use. If I were you I would not add any defocculant. Just add water, let it slake, and see how it turns out. (You can always add defocculant later.) I found both developed a really gross green mold, after years of sitting, so I would pass the slip through a screen before using it. I emailed the New York Dynamic folks at one point but wasn't impressed so I decided to try mixing my own again. I find EPK recipes to be more Seeley's like while English Grolleg recipes seem to be more Bell like. Good Luck - Thanks!
  4. I was recently asked about a pouring box for mold making. Here are two versions I use in the studio. The image with the bulbous object is my main pouring box. The pieces are 3/4" plywood cut into 5"x15" boards. I then screwed 1"x1" strips onto the ends which provide a lip for the small "C" clamps. Very quick and easy to assemble a box in any dimension. The second image shows another box variation that I use often for flat castings. The sides of the box are 2"x2" pieces of pine. (In his case I also used some 1"x2" strips.) The 2x2 pieces are labeled as "turning blanks" and come in a variety of wood types. (Woodworkers use them to make stairway balusters.) Because they are square and stocky they don't need much bracing other than a little clay at their base. The mold on the left I free formed and did not use the box to limit the plaster. (I shaped it by hand.) The mold on the right I filled the box with plaster and then ran a straight edge along the tops of the wood pieces which resulted in a mold that was evenly thick.
  5. Years ago I made plaster molds for a customer who then used my molds to make clay tiles. The clay tiles would be fired and then used as COOKIE molds. (The tiles had a slight relief that would make for very interesting cookies.) The process, I was told, was to lightly oil the fired tile and then place a little bit of cookie dough on it. Put both in the oven and bake for the normal amount of time. As the dough softened, and baked it, would lay down on the tile and take the relief. Then, once the tile cooled enough, the cookie would lift off the tile easily. I've often thought of making promotional cookies, for studio events, but haven't taken the time to do it yet. Making chocolates sounds fun but challenging. Let us know how it turns out.
  6. Looks like Lemon Grove is in southern CA, near the Mexico border. (If you google it you can actually see the storefront.) It appears to be located near a place called Plaster City. (A site producing plaster for USG.) Imagine setting up a mold making studio in Plaster City?
  7. I have mixed up the "Magic Water" recipe and it works. One gallon water, 9.5 gm sod silicate, 3 gm soda ash. Soda ash is quite caustic so make sure to wear gloves, or a glove, if you have a cut on your hand. It does sting otherwise. If I recall the "clay" content was 2/3 clay powder and 1/3 toilet paper.
  8. Hey Jeanne, I've had similar experiences. The Velvets are nice, because they don't cause the overglaze to dry out/pinhole, (as much) but they are thin. The LUG underglazes are nice, because they're more opaque, but they cause the overglaze to dry out sometimes. An alternative is to use the LUG White Underglaze, as a base, and then add Mason stains for color. This way you can control the intensity of the color and still have great brush-ability. While SOME Velvets/LUG underglazes do well at cone 6 I presume most are really intended for cone 06. By using LUG as a base, and adding your own Mason stains, you're creating an underglaze that can tolerate cone 6 and beyond. (possibly?)
  9. If you look in the Community Marketplace someone posted looking for a used slab roller. (In Boulder no less.)
  10. Years ago I found a book about Belleek porcelain. (I had never heard of the company before finding the book. Apparently, it's an old Irish pottery.) In the book they showed beautiful porcelain figurines. To allow for variety each appendage, arms and legs, were made with a ball end. The ball end fit into a socket on the main torso form. That way the arms and legs could be arranged in different ways. A huge pain to mold but I did this for the Akita mold. Each leg had a ball like end that fit into sockets on the main torso. As the piece was small there wasn't much room, to move each appendage, but it did allow the artist to play with it as he saw fit.
  11. I find it best to thin the underglaze to a heavy cream consistency. (or slightly thinner) When I open most underglaze jars they have a pudding like consistency. Even though the mixture is incredibly smooth I find it goes on incredibly thick. (Hence brush marks.) As well, I apply coats 5-10 minutes apart. (That way the surface is still slightly damp.) If I wait until the previous coat is completely dry I find it hard to prevent brush marks.
  12. Beautiful work Hyn Patty. Can't imagine molding it. Years ago a gent sculpted an Akita dog with as much detail. About the same size as your project. Nightmare project but he was happy with the molds when it was completed. (He was a breeder and brought several dogs when he picked up the molds. Super strong animals but very well behaved.) Have you ever heard of Breyerfest? For several years I worked at a pottery shop that made promo mugs for the event. Had no idea what it was until I looked it up. Here in Minneapolis the big collectible was little porcelain buildings made by Dept56. Had no idea there was another type of collectible out there.
  13. Hey Paula, How big is your plaster board and how old is it? You can "repair" plaster but I find it only works best with new plaster. Presumably your plaster surface has absorbed a lot of minerals, from wedging lots of clay, and that makes it less friendly to new plaster. If you want to try it simply mix plaster, into a milk like thickness, and pour it into the plaster holes. As soon as it loses its wet sheen use a sharp scraper to level off the surface. Do this procedure a few times until you have a smooth surface. It may not absorb as well as the rest of the slab but at least the holes will be filled. Also, is it not possible to flip the plaster board and use the other side as a new surface?
  14. Hello Karen, Can you post pictures? From my experience only plaster molds can be used with slip casting. I do know folks who have used rubber molds for pressing wet clay but that has its own challenges. I would recommend you make plaster molds, from your silicone molds, and then use the plaster molds to slip cast.
  15. Hey Samantha, Welcome to the Forum. The kiln looks great. The outside jacket looks fairly clean and the interior bricks look to be in good shape. The kiln floor looks to be in good shape. $450 is probably a good price these days. It uses a kiln sitter to control the kiln so that's just one aspect that you will need to consider. (You have to manually turn up the kiln throughout the firing process.) I've been firing a kiln, very similar, and have had no problems for 25 years.
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