Adam's Doll Blog

Misaki’s now wearing her first pair of sandals made from the newest wedge mold. The straps and thong piece are PVC.

My Summer Storm Misaki came with a pair of wedge sandals that are outrageously mismatched–one is wider than the other and shorter from front to back. The bottoms of the wedge soles are also hand carved, crudely. Clearly, shoes are not Integrity Toys’ strong point. Misaki fits in some of my large Momoko shoe collection, but she is really begging for some properly fitting shoes to call her own. To this end, I spent last week making a pair of general-purpose wedge soles that are custom fit to Misaki. Here I show how I make the symmetrical left-right pair.

The first think I do is make some rough “blanks” from Super Sculpey FIRM. I form the basic wedge shape, and press Misaki’s feet into them to make impressions. Pressing the feet into the Sculpey insures that the foot bed will properly conform to the foot after all the filing and shaping has been done to the baked part.

Here is my trick for making symmetrical pairs: I use a TINY amount of Krazy Glue to attach the blanks together at the soles. All profile carving will be done to both blanks at the same time.

Here you can see that I’ve been filing the conjoined blanks:

The result of my little trick is a closely matched left-right pair when the two blanks are separated:

As you can see in the above photo, when I carved the footbed area of the blanks, I deliberately left untouched spots where Misaki’s heels and balls of her feet impressed the Sculpey. Leaving these small depressions helps the final shoe to stay correctly positioned on the foot. Her feet naturally align themselves with the divots.

I’m leaving these soles with a bit of platform to them, so that a variety of shoe styles can be made from them. I won’t be using the resulting mold to produce only platform shoes, but it’s much easier to file castings down than it is to build them up. I will probably file away the platforms on a pair of castings and use them to make another lower-profile mold.

Satisfied with the symmetry of my carvings, I polish the shoe masters with a 3-way nail buffer, and set them up on Klean Klay for producing a silicone mold. The process of silicone mold-making is shown in greater detail in my previous blog entries.

Here is the finished mold:

The first castings in Smooth Cast ONYX fit perfectly. These wedge soles are now ready for uppers–the creation of which will be shown in a future post.

End.

Brace yourself for an über-lengthy, image-dense blog post full of Smooth-On products I purchased from their Boston distributor, Reynolds Advanced Materials.

In my last entry, I showed how I made a master model of a Momoko shoe from Super Sculpey. In this post, I will show the steps I use to make RTV silicone molds for casting the final product in polyurethane. This particular shoe project actually had two mold-making steps because my master Sculpey shoe was not left/right-specific. I first made a mold to reproduce the Sculpey shoe in urethane, then I carved two of the first-generation urethane castings to be a left and right pair. This pair then became the left and right masters for the final pair mold.

Shown below is a cutaway of the mold I used to make a direct copy of the Sculpey shoe from the previous entry. I made a dozen or so castings, then sacrificed the mold in the name of science , dissecting it with a scalpel. The mold I’m going to show in the making is just like this one, only it produces a left and right pair of shoes rather than just one.

Here on the left is a pair of shoes I made from the mold above, which are made lefts and rights only by the buckle placement–the shoes are otherwise identical and symmetrical. In the middle is the pair of castings that I have further carved (subtly) into a left and right handed pair. I shaped the toe section and arches. At the far right is a clear casting from the single-shoe mold that I consulted while carving the black pair, so that I would know where it was safe to remove material from. The black left and right pair are the master models for the final mold.

Here is a close-up of the clear reference shoe. You can see that there is a lot of material in the foot-bed area, because the momoko foot does not have bent toes or the normal proportions of a human foot.

Here is a side view of the prototype pair (left) and the left-right pair (right). The heels on the right pair look mismatched in thickness, but this is a camera perspective trick, I actually spent hours with my Mitutoyo digital calipers getting the shoes to be near-exact mirror images.

Here is the first step of the clay “layup”. I filled the arch spaces with Klean Klay, and placed them on the slab:

Next, I’m bisecting the slab to make it easier to carve details around each shoe:

First, I go all around the part line with this ball-end Sculpey tool, to that my part line for the 2-piece mold ends up on the bottom edge of the shoe. I’m slightly undercutting the model, so that the flash is actually on the very edge (easiest to trim off from there).

I like a clean mold, so I cut away displaced clay from the previous step:

One side done:

Both sides laid-up:

I then rejoined the slab on top of a lego plate piece, the bumps of which help to tie the clay halves together. I smoothed the seam. Also in this photo, you can see where I have super-glued on the wires that will form the air vents (risers), and I’ve placed the curved eye droppers that will form the pour holes (sprues):

Side view:

Next, the lego brick walls go up, to hold in the silicone, and the inside of the cavity gets a light coating of Mann 200 mold release:

Then, I mix up the Sorta-Clear 18 platinum silicone. I’m using Smooth-On’s Plat Cat catalyst also, to speed up curing time. I cure the mold at 150°F also, reducing overall cure time from the normal 24 hours to just 2 hours. I’m not patient, OK?

Stir like a mad fiend:

Transfer to larger container, so that no unmixed components get into the final mold, and because the silicone needs expansion room for the vacuum degassing stage.

Here I’ve poured the silicone into the mold, slowly. I give it about 15 minutes for the bulk of the bubbles to rise to the surface:

Then, the still-liquid mold goes into the pressure tank. I cure my molds at the same pressure I use during the polyurethane casting, about 50-60 psi. The air pressure insures that my mold will have no bubbles whatsoever. A single bubble can ruin a mold, so this step is worthwhile if you already have this equipment for pressure casting:

This mold is under 50 psi.

2 hours later, the top half of the mold is cured to solid rubber. I usually put the mold in the freezer at this point, to make it easier to remove the clay in one piece.

Here, I pulled off the clay:

All the clay is removed from the bottom of the mold:

And the legos are built up again to receive the bottom piece pour. Here I give it another spray with Mann Ease Release 200, to prevent the new silicone bottom piece from adhering to the already-cured top piece. This is important, you do not want to forget the release agent when making a 2-part mold!

A few more hours, and the mold is complete!

It comes apart at the seam, because of the mold release agent between the parts:

Here, I’ve taken out the pins and eye droppers:

First pour:

Here is the result of my first pour of Smooth-Cast ONYX into the new mold. It leaked a little out the toe end, but only because I skimped on rubber bands in order to have a clear video camera shot while filling the mold:

The excess is no problem, it just comes off as wafer-thin flash:

Out come the sprues, which I detached from the shoes by squeezing the mold. I engineer the sprues with a pinched  spot to insure that they break off about 2mm from the part, so that I don’t end up with a chunk out of the part:

Now I have two pairs! Polished high-durometer polyurethane masters make very good molds–the newly cast parts come out of the mold almost as shiny and glossy as the polished masters. And this is without a silicone release agent, which would shine them up even more (though in my experience, that comes at the expense of mold longevity):

This concludes my mold tutorial.

This post describes how I made one Momoko Doll shoe (1:6 scale) from Super Sculpey for reproduction via resin casting. I will refer to the finished Sculpey shoe as the “master” from which molds are made. In foundry speak, this is known as a “pattern”. This post details creation of this master–producing the RTV silicone mold and polyurethane castings will be covered in the next entry. Here is my current sculpting material of choice, Super Sculpey FIRM.

This is like the beige Super Sculpey sold in most arts and crafts stores, but it has a firmer texture. I found standard Super Sculpey too soft when warmed by my hands to make thin-walled parts from–my tiny sculptures were collapsing on themselves or deforming as I tried to smooth them. Super Sculpey FIRM is working much better. Also in this first photo, you can see some rough and finished masters or soles I made for an earlier shoe design.

Here (below) is how I start out. For this shoe, which is going to be a platform type, I start by cutting out a wedge of Sculpey and squishing it into a shape that matches the angle of my Momoko foot form (a rigid resin casting of a Momoko foot and ankle).

After massaging the Sculpey into a suitable wedge, I rolled some to about 3/32″ thickness and cut out a strip to form the back of the shoe. I use a 6″ polymer clay blade for these straight cuts.

I use the same thickness for the toe piece:

Next, I smoothed the pieces together with my fingers and ball-end Sculpey Studio tools, and trimmed away excess to form clean lines. It’s important to note here that the joins must be made with no gaps and very well blended, particularly in any areas that will be carved or filed after baking. If you are sloppy and only smooth over the surface, you will encounter the voids during the post-bake filing and carving, and will have to patch holes. For the same reason, it’s important to knead your Sculpey really well before you start, because you don’t want unblended folds or entrapped air inside your piece, because you will undoubtedly find them later…

Here you can see the stat of the piece just prior to baking for 20 minutes at 175°F. I have carefully extracted the placeholder foot and nudged the inside of the shoe all the way around the inside to enlarge it a little bit and make it symmetrical (this particular form will be used to produce both left and right 2nd generation masters via resin casting duplication and further carving).

Here we see the shoe-to-be after baking. It is fairly rigid PVC now, and can be filed, carved, sanded and ultimately polished. Here I’ve started to file it to final size already. Notice that the side and rear “walls” of the shoe are much thinner than in the above photo. They are about 1/16″ now, their final thickness.

The Sculpey shrinks a little when baked, but remember that I took the time to enlarge the inside of the shoe a little before baking. It doesn’t take much, shrinkage is on the order of a few thousands of an inch per inch. That said, it did not quite fit after baking–the toe was a little tight for the test foot, so I used the Dremel and a 1/8″ ball high-speed cutter to hollow out and make more symmetric the toe area. At this stage it needs to fit loosely, because when you make a silicone mold of a part, and cast it in resin, the resulting duplicate part shrinks about 0.001″-0.002″ per inch. Exact amount of shrinkage depends on the resin you use. In any case though, there will be some shrinkage so the master shoe must fit loosely. If you are making a shoe that will accommodate socks, then obviously it needs to be really loose. This shoe I’m making is for use on a bare Momoko foot, or one with thin stockings.

OK, here is where I put down my camera for a little while, and focused on the task at hand. You’ll have to excuse the lack of intermediate photos and just fast forward to the near-finished master. What has transpired in the two hours since the last photo above is cutting of the sole with a coping saw, plus copious amounts of filing and sanding to the final shape. Lastly, I used a scalpel to cut a fine line all the way around the shoe to demarcate the sole from the upper. When I say lots of filing, I mean LOTS of filing! After sanding, I use a 3-way nail buffer from CVS to polish the master before making a silicone mold. This improves surface finish on the cast parts.

This concludes the Sculpey master process. I’m skipping ahead now–skipping the entire lengthy process of producing a silicone mold and pressure casting duplicates–to show you the results. Making silicone molds and casting plastic parts will be the subject of a future post. The red shoes are the first test casts from my mold. I used a very fast setting polyurethane for these tests, Smooth-On’s Smooth Cast 300Q with red dye added. The final shoes will be cast in black Smooth Cast ONYX, a stronger but slower setting product which cures hard enough overnight to be polished to a high gloss shine.

At this point in time, I chose to make a full prototype pair with strap and buckle. I’m not quite done though, as I intend to further carve a set of castings to produce distinct left and right shoes with subtle sole curvature differences, which I will use to make a pair mold (one silicone block mold which produces left and right shoes in a single resin pour). The strap is black PVC craft lace (gimp) and the buckle is made from silver-plated wire from the jewelery section of A.C. Moore or Michael’s (I forget which and it doesn’t matter). The strap is glued on at the non-buckle end, and the buckle wire goes into a drilled 0.028″ hole on the other side to form a simple pin type closure.

Here is a comparison shot with the classic Barbie MJs that Blythe has made so popular:

And here are my new shoes on Momoko (doll on the left):