Molding and casting by Kayakasaurus

[Doug Watson]

Well I'm finally casting! Thank you to Doug and Reinier for your help! The first two each had unique problems of their own... That's why you see them from the top. But I have the amount of resin down and my third cast came out 95% perfect, even the club turned out. It's only problem is an air bubble in the front right foot. Here he is! BTW I sprayed some grey primer on to see the details.

You are welcome. Those look pretty good, not much flash around the mould lines. If that air bubble is at a mould break you can Dremel a new vent channel over to an existing vent with a barrel shaped high speed cutter, tungsten is best.
Looks like you are on your way, go forth and multiply.

[reinier zwanink]

Congrats kaya
Looks very good to me
Airbubble in its toe?
Just make a small cut above it and mangle the mold a little on that point
That will almost always do the trick

[Kayakasaurus]

Hello Doug Watson!

I'm going to be making a mold for a small ceratopsian. Do you have any pics of any of your ceratopsians in a mold? Any tips for the frill and horns? Thank you!

[Doug Watson]

Hello Doug Watson!

I'm going to be making a mold for a small ceratopsian. Do you have any pics of any of your ceratopsians in a mold? Any tips for the frill and horns? Thank you!

I don't have any pictures, I'll see if I can dig a mould out of storage and put something together.

[Doug Watson]

Okay here are 4 shots I hope will help you. Deciding how to divide a mould can be the hardest but most satisfying part of mould making. I just sit down and look for places where the mould will lock. The more practice you get the better you will be at it. I start out hoping for a two piece but if I find that will compromise the cast I go for more pieces.
On the Nasutoceratops in order to vent the shield all around plus vent the brow horns I went with a three piece mould, two sides and one piece covering the tops of the brow horns and the shield. If it didn't have the brow horns but had a nasal horn it could be done in two pieces but one half of the shield would not be vented.
Be sure to connect the vents and key from the third piece to the 1st and 2nd piece.

Right side with 3rd piece in place.



Right side with 3rd piece removed.



Left side with 3rd piece in place.



3rd piece by itself.

[Newt]

Thanks for posting, Doug! That's very helpful.

[Kayakasaurus]

Great pictures thank you! Did you mean to say Diabloceratops? My sculpt is only 3 inches long and it has brow horns. I've gotten two good castings from my Shunosaurus but it is leaking really bad now. It has the key plus a plaster jacket that I clamp down nice and tight, but it still puddles. How do you seal your mold halves? I think my mold is to flimsy, so I'd like to try a 2-3 part block mold for my next one, it's a little more silicone but the silicone is a little less expensive. And I'd like to invest in sturdy easy to use molds. Could you tell me the average life expectancy for a platinum cure mold i.e. How many casts it can produce?  Thank you for your time!

[Doug Watson]

Great pictures thank you! Did you mean to say Diabloceratops? My sculpt is only 3 inches long and it has brow horns. I've gotten two good castings from my Shunosaurus but it is leaking really bad now. It has the key plus a plaster jacket that I clamp down nice and tight, but it still puddles. How do you seal your mold halves? I think my mold is to flimsy, so I'd like to try a 2-3 part block mold for my next one, it's a little more silicone but the silicone is a little less expensive. And I'd like to invest in sturdy easy to use molds. Could you tell me the average life expectancy for a platinum cure mold i.e. How many casts it can produce?  Thank you for your time!

Oops, I meant Nasutoceratops. If there is a space between the plaster jackets like a Oreo cookie where the rubber is the cream you should be able to get a tight fit. You can actually clamp it too tight and cause distortion and leaks, that might be the problem, I just use wide elastic bands. The silicone rubber I used to use was cured with Dibutyltin Dilaurate so I am not familiar with platinum cure rubber, maybe someone else here is. It could be just that it is a Smooth-On product as I mentioned I wasn't happy with their urethanes. Silicone is usually good for many casts and can last for years but even they break down over time especially on undercuts. In the past I have repaired silicone moulds to maintain their lifespan. If a chunk of rubber gets ripped off retrieve it and use some silicone caulking to glue it back on. Do this on tears as well.
For my block moulds I still make a support jacket out of 1/8 hardboard for each side (just traced to shape and cut out) because even the block moulds can distort when under tension.

[Newt]

I've read in various places that platinum silicone molds can produce up to 50 casts, if used gently (e.g., use mold release, let the molds cool between casts).

[brandem]

That's interesting I've not really had a problem with casts holding their integrity for a considerable amount of time

[Kayakasaurus]

Well I like things to be clean cut and solid, so I think a block mold is for me I'm new to molds but I thought silicone was either platinum cure or tin cure. And I read platinum has a longer life so I went with it. It's good to see people joining in on the conversation  Doug, do you know what the commercial molds look like? I guess those would be over seas?

[Kayakasaurus]

Hello, another request for Doug Watson.

Could you please post some pics of your Sauropelta mold? That would be very helpful! I am wondering if you vented the spikes, or how that works. Thank you

[Doug Watson]

Well I like things to be clean cut and solid, so I think a block mold is for me I'm new to molds but I thought silicone was either platinum cure or tin cure. And I read platinum has a longer life so I went with it. It's good to see people joining in on the conversation  Doug, do you know what the commercial molds look like? I guess those would be over seas?

Sorry for the late reply but I didn't see this question until today. The commercial moulds for toy production are metal and cost in the thousands to produce (P.S. I haven't seen them in person).

[Doug Watson]

Hello, another request for Doug Watson.

Could you please post some pics of your Sauropelta mold? That would be very helpful! I am wondering if you vented the spikes, or how that works. Thank you

I could do that but you know the way I learned once I had the basics of mould making was by trial and error. What I would prefer would be for you to show what you want to mould and tell me how you would do it. I would be happy to comment then and perhaps illustrate what I mean by showing my mould like I did before that way you work it out and learn from the  experience. Hopefully I get the notification the next time you post here I missed the last one in May.

[Halichoeres]

sub, for pure curiosity.

[Doug Watson]

sub, for pure curiosity.

In case you haven't seen them in replies 48 & 84 of this thread I have already shown my Apatosaurus and Nasutoceratops moulds. (the fact the numbers of the replies are the reverse of each other is serendipitous).

[Kayakasaurus]

Good to hear from you! No Prob about the last post, I found a video on commercial molds. The reason I didn't post my sculpt is because I wasn't planning to show anyone yet. I've just finished three commissions, the way it worked out is sort of like a partnership, where the money goes to the mold making materials. If it was my own money, I'd feel a little freer to experiment lol. Anyways, here is one way I thought of venting the horizontal spikes along the side by making a 3 part mold. The problem is the vertical spikes along the back aren't vented, and I still need to get the horizontal spike vents along the side to come out vertically by the feet. What do you think?

[Doug Watson]

Good to hear from you! No Prob about the last post, I found a video on commercial molds. The reason I didn't post my sculpt is because I wasn't planning to show anyone yet. I've just finished three commissions, the way it worked out is sort of like a partnership, where the money goes to the mold making materials. If it was my own money, I'd feel a little freer to experiment lol. Anyways, here is one way I thought of venting the horizontal spikes along the side by making a 3 part mold. The problem is the vertical spikes along the back aren't vented, and I still need to get the horizontal spike vents along the side to come out vertically by the feet. What do you think?

Okay, you know you can PM me and I can give you my e-mail if there is something you don't want to post online. I am good at keeping secrets.
I think you may have to go for more pieces to catch the vertical spikes. Let me dig out my mould and I'll see what I did. I'll post some shots again here. I am pretty sure I cast from the tip of the tail that way you can run your vents from the ends of the spikes and have them all exit by the tail. Give me a day or two to dig out my mould. I have done a bunch since then so its easy to forget exactly what I did.

One other thing for casting, I read for the Shunosaurus in reply # 79 I guess there was some hit and miss on the amount of resin to pour. Have you tried water displacement? Fill a bucket to the brim with water and submerge your original model. Measure the amount of water displaced and that will give you a good idea of the volume of resin to mix. I include my thumb and forefinger to account for the sprue and vents.

P.S. I forgot to mention when you do this have your bucket sitting in a larger pan to catch the displaced water. Then you just pour the water in the pan into a cup and that gives you the displaced volume.

[Doug Watson]

I dug out my Sauropelta mould and I was right I cast it from the tip of the tail and it was done in 5 pieces.
Here are some shots. Remember each section will need a continuous running key where it contacts other pieces to avoid slippage. Also you will have to connect your air vents to each piece running them up to exit by the tail.

Mould blown apart to show the 5 pieces.



First section takes in back of Sauropelta up to the halfway point of the most dorsal spikes and the most dorsal plates on the side of the tail.



Second & third sections added. These cover the space between the more dorsal and more ventral spikes plus between the more dorsal and ventral plates along the tail



Forth section added that splits the Sauropleta along the legs and covers the remaining sides of the spikes and plates on one side. The fifth section finishes off the other side. The five V shape notches that you see along the bottom of the mould correspond to notches in the hardboard I use for support and hold elastics in place that hold the mould shut.



I have just added a shot of the mould put together with the hardboard supports on two sides. Since my sides weren't flat I hinged each board with duct tape. Hope you can figure this out from these, if this is your first more than two piece mould you sure jumped to the head of the difficulty line.

[Kayakasaurus]

Here is my finished 3-part Hylaeosaurus mold.