Molding and casting by Kayakasaurus

[Kayakasaurus]

Guess what?? IT DOSE'NT WORK WITH SCULPEY EITHER!!! Well I got that out of my system. From all the tests I did it works best with the Magic sculpt as well as the acrylic paint. Those are also the only materials that weren't soft. It also works on all the metal buttons I've been testing on. This sure is tricky and I'm not very impressed with "Dragon skin". However I did find red food coloring works great! So if nothing is working maybe I will go ahead and use Jolly King and put clear acrylic over it since it seems to like acrylic.  BTW if you ever need an apartment in the States you know who to call   LOL

[Doug Watson]

Guess what?? IT DOSE'NT WORK WITH SCULPEY EITHER!!! Well I got that out of my system. From all the tests I did it works best with the Magic sculpt as well as the acrylic paint. Those are also the only materials that weren't soft. It also works on all the metal buttons I've been testing on. This sure is tricky and I'm not very impressed with "Dragon skin". However I did find red food coloring works great! So if nothing is working maybe I will go ahead and use Jolly King and put clear acrylic over it since it seems to like acrylic.  BTW if you ever need an apartment in the States you know who to call   LOL

Have you tried sealing the Plastilene with a couple coats of shellac yet?

[Kayakasaurus]

Oh yah I forgot I'll check on that... But whatever I use, I'm gonna seal the heck out of it I started applying clay and it's lots of fun. Here are some pics. Is this how you would do it? Where would you recommend the airways and sprue? If this works I can't wait to do my Centrosaurus! I've updated his eyes since I got the magic sculpt.

[reinier zwanink]

Remember to keep your clay as smouth as possible but do include at least 2 nobs sp you can aline the sides
If you dont it will not seal properly giving deforming and leakage
You can cast it back down with the feet as fill and airholes
But do add 2 ventways in the tail
1 at the tip and 1 half way at its lowest point

[Kayakasaurus]

Thanks Reinier! How does this look?

[Doug Watson]

Thanks Reinier! How does this look?

This is how I would do it.
Only have a mouse so its a little rough.
Solid outside line = outer edge 
Thick solid piece under Left rear foot = sprue, you don't need a sprue under each foot
Broken line = continuous key. Can be done as a negative or a positive at this stage. Even though I show it as a broken line it should be solid. The deeper or higher you make it the better the lock. You can do those squares if you want but not needed with a continuous key.
Thin solid inside lines = are the air vents. You need to vent the right front foot the line to the left of the vent for the left front foot is going to that foot. Vent any long claws or spikes. Should also vent the belly, just noticed I left that off.

[Doug Watson]

I have been looking at the divide on your right front leg, it has bothered me from the start. I would have the leg exposed behind the left front and fill in the area that you have left open in front of the leg. After your rubber is cured you are going to have to dig the clay out of a thin wedge and then squeeze rubber into that void. The way I would separate it you would see all four legs looking down from above.

[Kayakasaurus]

I have been looking at the divide on your right front leg, it has bothered me from the start. I would have the leg exposed behind the left front and fill in the area that you have left open in front of the leg. After your rubber is cured you are going to have to dig the clay out of a thin wedge and then squeeze rubber into that void. The way I would separate it you would see all four legs looking down from above.

Sounds good! I have no idea what I'm doing I just guessed based on your Smilodon. I'll change it and do the channels tomorrow. Thanks for the help 

[Doug Watson]

My Apatosaurus has almost the same leg positioning so I popped it back in the mould to hopefully help illustrate what I mean.

This shot shows it in the right side of the mould the way you have yours set up, should illustrate what I mean for the legs. In this side the continuous key is a negative.



This shot shows it in the opposite or left side of the mould. In this shot the continuous key is a positive. The negatives that you see are the vents & sprue.



This is a detail of the left side. From the left side edge you can see the raised ridge that is the positive side of the key. The beauty of this type of key is it locks the two pieces everywhere to prevent slipping plus when you are pouring plastic with the consistency of water it prevents leaks as it works as a dam. The negative trough to the right of it is an air vent. The big negative under the foot is the pouring sprue. When you are using gravity the taller or more mass to the sprue the better. For the vents it is okay for the vents to cut through the key you just don't want the key to cut through the vents if you know what I mean. I make a continuous key all around and then cross my vents through if it is needed. In this case and it is what I do now most of the time I feed all my vents alongside the key to a central exit point with the sprue so I don't have to cut through the key. The way you have yours set up you would need to cut through the key. All you need to do is extend the area around the sprue and feed them all there like I have done. I also sprued it on a front foot so there was a downward angle to the pour adding pressure to get the material to the tip of the tail.

[Kayakasaurus]

Thanks for the great pics. I've changed the leg as you suggested. I need to clean the model a little around the edges were the clay started filling in between scales and then I'll do the channels

[Kayakasaurus]

Ok I did the channels I just have three questions.

1. I think I should do the front left foot when I do the other side sense it's claw is buried in clay right now.

2. I'm not sure how to do the belly without making a little wall for the channel to go up. When I flip it over I would dig the wall out but leave the channel.

3. How would you do this spike that comes out from the side? All four spikes are horizontal and the last pic is the only thing I could think of and it seems like it wouldn't work.

Ok I haven't fully attached the channels but if you think they're in the right place then I will. Then I'm ready to seal and pour!

Edit: I have added the channel for the head

[Doug Watson]

Ok I did the channels I just have three questions.
1. I think I should do the front left foot when I do the other side sense it's claw is buried in clay right now.
2. I'm not sure how to do the belly without making a little wall for the channel to go up. When I flip it over I would dig the wall out but leave the channel.
3. How would you do this spike that comes out from the side? All four spikes are horizontal and the last pic is the only thing I could think of and it seems like it wouldn't work.
Ok I haven't fully attached the channels but if you think they're in the right place then I will. Then I'm ready to seal and pour!
Edit: I have added the channel for the head

Okay I just modified this post again, I think I am still sleepy from cooking last nights Easter supper. The more direct vents the better I have modified your image again with dotted lines for the vents my original notes follow.

1. I would dig that claw out now and vent it. It is a lot harder to add a vent to a rubber side plus it will be cleaner this way (dotted line in attached image)
2. Just bring the clay between the right front and right rear up to a peak under the belly like the peak on a roof and run the vent along the peak (dotted line in attached image)
3. The way you have vented it in the last shot will work but you have three spikes not four correct?

I like my moulds to be as clean and precise as my sculpts. Right now it looks sloppy. I would make my outer edge a sharp even line, you could remove some excess clay above the back of the model I like to have a fairly even distance between my key and the outside edge that will also save on material. I would clean any excess clay off of my model with acetone or varsol whatever dissolves this clay. Acetone works well on Plasticine. You want a nice crisp line around your model where the clay meets it. For your key the deeper and better defined it is the the better the seal. I would add material behind and deepen it and widen it evenly. Plus it is okay the butt the key up against the vents, I have illustrated that in this image below (solid lines). Also the sprue should extend to the mould edge and don't be afraid to bulk it up you want a good sized pour hole because a restricted hole will just slow your pour down, have a look at my smilodon. I have a dotted line for the vent from the head that you say you have added.

[Doug Watson]

One more point I forgot to mention. To avoid having to prop moulds up I always engineer a flat spot on the bottom edge of the mould or support jacket so the mould sits flat on the table or pressure pot when I am pouring. Since you are doing a plaster style jacket you can embed some popsicle sticks or something like that to act as supports if you need them.

[Kayakasaurus]

Hello

I decided to dig out the front left claw from behind the foot instead of in front because the claw is at the back. I'll try Vaseline when I get everything in place. There are four spikes on the tail. They are all horizontal two on each side. I have two with channels to them and that third channel just goes to the top pf the club so I probably don't need it. So two spikes are in the clay on the other side, is that ok or is there a way to vent those from this side too? I think I'm going to have to add a wall around the whole thing. This mold making is tricky.

[Doug Watson]

Hello
I decided to dig out the front left claw from behind the foot instead of in front because the claw is at the back. I'll try Vaseline when I get everything in place. There are four spikes on the tail. They are all horizontal two on each side. I have two with channels to them and that third channel just goes to the top pf the club so I probably don't need it. So two spikes are in the clay on the other side, is that ok or is there a way to vent those from this side too? I think I'm going to have to add a wall around the whole thing. This mold making is tricky.

That's looking a lot better.
I went back and had a look at your sculpture in your other thread and now I get your club. By the way from the papers I have on Shunosaurus I interpret it to have three spikes. One at the tip of the tail and two before it on the dorsal surface. You can mould yours and vent all of the spikes by shifting the plane of the mould dam perpendicular to the rest of the dam when you get to the spikes. You will have to dig the ones out at the back. You should be able to hit all the spikes and the tip of the tail with a little patience.
Also since liquid always follows the path of least resistance I would keep the vent for the left rear foot and the tail separate and bring them both straight to the same level as the rest like I showed or the escaping air an liquid will be going out that back vent before the rest.
I still think you should seal your clay with shellac or some other plastic film.

[reinier zwanink]

I got some experience with casting but figures is something diffent
You got great help with watson here
But one prob thou
Asuming you cast legs up
There is a airtrap at the rear end now
Its the section directly behind the rear legs and the beginning of the tail
Where its "exit" would be

[Doug Watson]

I just checked the Technical Data sheet for Dragon Skin and this is what it says about sealing the mould dam and model. Did they give you one with the product?

"Cure Inhibition – To prevent inhibition, one or more coatings of a clear acrylic lacquer applied to the model surface is usually effective. Allow any sealer to thoroughly dry before applying rubber. Note: Even with a sealer, platinum silicones will not work with modeling clays containing heavy amounts of sulfur. Do a small scale test for compatibility before using on your project."

So according to the manufacturer you should at least be sealing the clay with a couple coats of an acrylic lacquer.

As to Reinier's comment he is right it wouldn't hurt to add more vents along the tail or anywhere else where air could get trapped. Even if you miss a spot if you have a Dremel or a Foredom you can use a tungsten cutter to carve extra vents into the rubber as long as the trap is along a mould break.

[Kayakasaurus]

Yes I did read that and that is what I'm planning to do. LOTS of sealer! I have some more tests prepared and I was glad to see they recommend sealing to solve the problem so I don't have to buy more clay. I guess I didn't do very good research on the Shuno  you should see my first dinosaur though... It resembled a stegosaurus if you squint. I'll make the adjustments including what Reinier pointed out.

I got some experience with casting but figures is something diffent
You got great help with watson here
But one prob thou
Asuming you cast legs up
There is a airtrap at the rear end now
Its the section directly behind the rear legs and the beginning of the tail
Where its "exit" would be

Good eye! I'll do that, thanks!

[Kayakasaurus]

Another step closer! I redid those vents that were wrong and added one where Reinier said. Here is what I came up with for the tail club. I'm almost done tricky but fun. If I can't find acrylic lacquer maybe I'll pick some up from the store. Vaseline first though!

[Doug Watson]

Another step closer! I redid those vents that were wrong and added one where Reinier said. Here is what I came up with for the tail club. I'm almost done tricky but fun. If I can't find acrylic lacquer maybe I'll pick some up from the store. Vaseline first though!

I am wondering why the vaseline, is it to smooth your clay? Looks fine to me, just smooth any rough bits with a tool, clean the clay from the model with some solvent and seal it with acrylic, then apply mould release.  You can use the solvent that you clean your model with to further smooth your clay before the acrylic if you wish.