Molding and casting by Kayakasaurus

[Kayakasaurus]

I'm posting this question here sense you guys use paint & epoxy to customize figures. I have this stegosaurus I sculpted from "Epoxy dough free form earth" by smooth on. I sprayed it with a coat of primer(as usual) and then painted it with various brands of acrylics such as Americana. As you can see in the close up photo, the stego, not that long after painting (days,weeks) developed these yellow sticky spots. I wiped them of with a wet paper towel and they came back again later. It seems like some sort of chemical reaction but I'm not sure what caused it. Has anyone experienced this? It keeps coming back!! Help!! Is there maybe a sealer I could spray it with?

[tyrantqueen]

I haven't heard of that brand before. I would recommend sending an email to the company. I did a google search and they claim that their product can be painted with acrylics, so something is obviously wrong What brand of primer are you using?

Btw a good brand to try is Aves.

[paleoferroequine]

   I don't know that brand either, I use Magic Sculpt.  However, if I were to guess it might be be that the putty wasn't mixed thoroughly enough. It might have seemed like it was but maybe some of it wasn't and it reacted with the paint. See if it seems a bit soft there. If so. scrape it off and seal it with super glue and add new putty if required. That's all I can think of.

[reinier zwanink]

I think its indeed your mix
With old resin the reaction is identical
It happens when its poorly mixed
but when they are smal (in your case it seems)
It happens to the B component (that is your hardner)
Sometimes you get little hard pieces that sort of die of but still hold harder inside it
That will leak out in  your model
Only thing you can do is drill out or let it leak for years

I got 1 here that did it for more than 7 years now

[Doug Watson]

I agree with reinier zwanink and paleoferroequine that it was probably your mix. I will sometimes do a bad mix myself especially if I only mixed a small amount at that time. I don't paint mine so I haven't seen the seepage but I have had areas that didn't cure properly. One thing I do is I always try to keep a small amount of my mix unused so that I can check it's hardness the next day. If it is still soft I will check my model to see if any areas are soft. When you find a soft area it is best just to carve it out and redo it.

I am very familiar with Smooth On casting resins and moulding rubbers but I have never used their epoxy clays. One thing I will warn you about, never use Smooth On PMC-724 urethane moulding rubbers for a mould you want to keep. Over time with the moisture in the air they will break down into an unusable goo. Then you have disposal problems. We did a bunch of moulds at the museum that all started to break down after a few years. Their silicones should be fine but stay away from the urethanes. I use the Polytek  urethane rubbers and I have moulds that are 23 years old and still in fine shape

[Kayakasaurus]

I think its indeed your mix
With old resin the reaction is identical
It happens when its poorly mixed
but when they are smal (in your case it seems)
It happens to the B component (that is your hardner)
Sometimes you get little hard pieces that sort of die of but still hold harder inside it
That will leak out in  your model
Only thing you can do is drill out or let it leak for years

I got 1 here that did it for more than 7 years now

I think you got it. It's the hardner. I recognize it now, it's the same goo it develops in the container on the parts exposed to air. The spots arn't soft either. It seems to be in small random patches all over the model. Funny that they didn't appear until after I colored it because I had it primered for about a month. I am looking forward to switching over to magic sculpt. Thank you all!!!

[Kayakasaurus]

Ok, I have some questions about mold making and casting. I would like to cast some of my models in the near future and I'm ready to order supplies. I'm thinking along the lines of this tutorial: http://m.instructables.com/id/2-Part-silicone-mold/

I have a few questions...

Which brand of silicone? Smooth-on?

Is their a plastic I can cast with that would have a little give to it like a toy?

2 or 3 part mold?

Please share things you've learned from mold/casting!

I would like to make a line of accurate 1:30 scale models(Toys) starting with my Shunosaurus because of its simple anatomy. as I make more Dinosaurs I could add my favorites to the lline. Thank you for any tips!

[reinier zwanink]

We a 2 part mold is the best
I have used 3 part molds but they never aline properly and that would make your model a loss.
looking at shuna it it possible to make a 2 part mold and cast it i one piece

You only have 1 problem
To get the best details you will need a vacuüm unit but that is expencive
So you will need to "rub" the details with resin first then close the mold and fil it up

[Doug Watson]

Ok, I have some questions about mold making and casting. I would like to cast some of my models in the near future and I'm ready to order supplies. I'm thinking along the lines of this tutorial: http://m.instructables.com/id/2-Part-silicone-mold/

I have a few questions...

Which brand of silicone? Smooth-on?

Is their a plastic I can cast with that would have a little give to it like a toy?

2 or 3 part mold?

Please share things you've learned from mold/casting!

I would like to make a line of accurate 1:30 scale models(Toys) starting with my Shunosaurus because of its simple anatomy. as I make more Dinosaurs I could add my favorites to the lline. Thank you for any tips!

Any brand of Silicone should be good and if you want to do multiple casts you should use silicone.

If you plan on doing production runs then you should de-gas your rubber with a vacuum pump and a pressure pot and pressure cast your resins in a pressure pot with a compressor, that is what I do but as reinier says all that equipment is expensive. If you are not pressure casting there are urethane casting resins like Polytek EasyFlo 60 that have the viscosity of water and should go into the crevices but you will need to add vents to your extremities to evacuate air or you may get trapped air and air bubbles in your cast.

I have made moulds of my pieces up to 5 parts but I make a continuous key around the sections to lock the parts. However your Shunosaurus can be moulded in two parts.  I would separate it the way I have partitioned my smilodon in this attached image. I looked at that tutorial and in my opinion that was a strange way to divide that stegosaurus. You want to avoid locks that will prevent you from separating your mould from your cast.
In my image I have separated the smilodon halves with plasticine and my continuous key is the furrow running around the outside nearest the wall. When I pour my second half I will let the furrow fill in to make the key. I have also run vent channels to the extremities and added a pouring sprue to the bottom of the left front foot. When I pour my second half those vents and the sprue are still present so they will be a void in the mould. In the case of the smilodon I also did a separate mould piece for inside the mouth.

If you use silicone make sure you do not use a sulphur based clay because that will inhibit the cure of your rubber and be sure to test and use a release agent on your model so the rubber does not glue itself to your model and use the release agent between your mould pieces. A silicone based mould release is usually best. I also seal my plastine with a liquid plastic film of my own making before I apply the release agent. A shellac will work as well.

Be sure to read the instructions and Material Safety Data sheets for all your materials. Preferably this work should be done in a fume hood or use good ventilation or a respirator, gloves etc if the MSDS calls for it

[Newt]

I will be delving into the world of molding and casting myself later this year, so I'm very glad to see this thread and great information from more experienced folks. Thanks!

[amargasaurus cazaui]

It may be off topic or require another thread, but I find myself curious about several things here Doug, and am enjoying your explanation of the process.
I wanted to ask, and if its all like double top secret information I understand but....
I purchase alot of dinosaur replicas and one thing I would like to understand is the gaps I do not know in the production process . In other words....you sculpt your subject, and create a single piece that is a sculpture then, I assume. It appears at that point you then make a resin master that you would paint and submit to Safari for production?So some of my questions would be ....as you sculpt the animal at what point and how do you obtain consultation on the figure? Do you take photos of the sculpt as it progresses and submit them to the particular consultant who states any corrections or adjustments, so you can sculpt them in or is the consultation portion all done prior to sculpting? Once the sculpt is finished, is that when you build a mold and cast it to get a mold to create a resin master with? Are the resin masters then painted before submission to Safari? Do they take your resin master, and create a mold that repeats the same something like fifty times in a sheet to print the run of the figure? How does the mass production part of it all happen once it leaves your hands? tons of questions I have here as you see...can you fill in some of the blanks?

[Kayakasaurus]

We need an "Ask Doug Watson" thread.  I have another question;how do the toy companies label the figures belly with such a small embossed font? Are you involved in that process Doug? I really want to find a way to label my models... Even if it has to be engraved.

[Doug Watson]

It may be off topic or require another thread, but I find myself curious about several things here Doug, and am enjoying your explanation of the process.
I wanted to ask, and if its all like double top secret information I understand but....
I purchase alot of dinosaur replicas and one thing I would like to understand is the gaps I do not know in the production process . In other words....you sculpt your subject, and create a single piece that is a sculpture then, I assume. It appears at that point you then make a resin master that you would paint and submit to Safari for production?So some of my questions would be ....as you sculpt the animal at what point and how do you obtain consultation on the figure? Do you take photos of the sculpt as it progresses and submit them to the particular consultant who states any corrections or adjustments, so you can sculpt them in or is the consultation portion all done prior to sculpting? Once the sculpt is finished, is that when you build a mold and cast it to get a mold to create a resin master with? Are the resin masters then painted before submission to Safari? Do they take your resin master, and create a mold that repeats the same something like fifty times in a sheet to print the run of the figure? How does the mass production part of it all happen once it leaves your hands? tons of questions I have here as you see...can you fill in some of the blanks?

Unfortunately I am not at liberty to talk about the process. How I do my moulds is the same for any moulds I do so I feel free to give advice on that since those methods are my own. 

[Doug Watson]

We need an "Ask Doug Watson" thread.  I have another question;how do the toy companies label the figures belly with such a small embossed font? Are you involved in that process Doug? I really want to find a way to label my models... Even if it has to be engraved.

I asked that question myself one time but unfortunately the person I asked didn't know. My guess was the letters were laser cut into the metal moulds but that wouldn't explain how they did it back in the old Marx factory in the 50s & 60s, maybe they employed and engraver. The only way you could do it would be either to sculpt them on your model or get small plastic letters and glue them on. The plastics shop here used to sell small individual plastic letters but they weren't that small, maybe someone out there makes some.

Just did a quick search and this site http://railwaymodels.tripod.com/ sells styrene letters as small as 2mm high, that's pretty darn small. I assume when they say high they mean the height of the letter not the thickness but you would have to check.

[Kayakasaurus]

Unfortunately I am not at liberty to talk about the process. How I do my moulds is the same for any moulds I do so I feel free to give advice on that since those methods are my own. 

I have a question about sculpting with magic sculpt. Do you usually go from start to finish sculpting the whole model? How do you hold the model and avoid smashing scales you've already made? or do you just do certain parts and let them harden before doing the rest? I have been avoiding this by hot glueing the armature feet to a piece of wood and doing half one day and then half the next day, holding onto the parts that have cured. Is there a better way? thank you for answering these questions it really helps!

[Doug Watson]

I have a question about sculpting with magic sculpt. Do you usually go from start to finish sculpting the whole model? How do you hold the model and avoid smashing scales you've already made? or do you just do certain parts and let them harden before doing the rest? I have been avoiding this by hot glueing the armature feet to a piece of wood and doing half one day and then half the next day, holding onto the parts that have cured. Is there a better way? thank you for answering these questions it really helps!

Normally I am working on anywhere from 3 to 7 pieces at a time so I do exactly what you guessed. I start at one end usually the rear and complete just enough so that I still have some unfinished area to hold on to. Then I go on to another piece, when that section is cured you are home free since you now have the entire rear end to hold onto. Sometimes if I am only working on one piece or it is really small I will glue a wooden dowel into the centre of the belly and hold onto that. The way I work I carve a foam form in the rough shape of my piece and that forms my armature so I have the foam to glue the dowel into. I can use the dowel to stick into a block of foam or a vice when I am not working on it. When the piece is done I cut the dowel and Dremel what is left down and then finish off the depression with magic sculpt.

[Kayakasaurus]

.

Here is the silicone I'm considering buying from Amazon. It's oomoo 25 and it cures pretty fast. It also says no vacuum chamber required. I picked the trial size because it's under $100 and It will be an experiment. I wish I knew someone locally that could help with molding
http://www.amazon.com/Smooth-On-OOMOO-Trial-Unit-Pint/dp/B00H3QO7K8

Thank you Doug I will be useing your smilodon mold for reference!

Here is the mold release I picked out. Look good? http://www.amazon.com/gp/aw/d/B004BNAN3G/ref=pd_aw_sim_hg_4?refRID=0Q6SB0JM26HAC3KMMZ7E

If I can make a successful mold and cast it then maybe I can try Kickstarter. I would have a final product and more sculpts ready to cast I would just need money for silicone/plastic and equipment.

[brandem]

Oomoo is good but has its issues when not casting flatish objects, any smooth on product is available throught thier website in a trail size so there are several options there

[Doug Watson]

Here is the silicone I'm considering buying from Amazon. It's oomoo 25 and it cures pretty fast. It also says no vacuum chamber required. I picked the trial size because it's under $100 and It will be an experiment. I wish I knew someone locally that could help with molding
http://www.amazon.com/Smooth-On-OOMOO-Trial-Unit-Pint/dp/B00H3QO7K8

Thank you Doug I will be useing your smilodon mold for reference!

Here is the mold release I picked out. Look good? http://www.amazon.com/gp/aw/d/B004BNAN3G/ref=pd_aw_sim_hg_4?refRID=0Q6SB0JM26HAC3KMMZ7E

If I can make a successful mold and cast it then maybe I can try Kickstarter. I would have a final product and more sculpts ready to cast I would just need money for silicone/plastic and equipment.

I haven't used that silicone rubber or release but the release looks like it should work. When you start casting you may want to use a paintable release since it can be hard to get all of a nonpaintable release off of a cast before painting. I use Polyease 2500.
To tell the truth when I use silicone rubber because it is so darn expensive I make skin or brush on moulds with plaster or FRP support jackets to save on material. I only pour block moulds with polyurethane rubber because it is so much cheaper and I am not making many casts. A skin mould is a more advanced form of mould making but your set up is the same as I did for the smilodon except you don't need as high a wall around the piece. I would make the wall the height I want for the thickness of the rubber on the flange. Here is a step by step skin mould process using Dragon Skin silicone from Smooth On http://www.smooth-on.com/gallery.php?galleryid=208. The main difference from the way I make my skin moulds is that after I have my detail covered with cured rubber I add polyester cheesecloth to the next 2 layers of rubber to strengthen the mould and prevent tearing. Once one side is done you need to make a support jacket for that side before flipping it over and removing the plasticine dam because your flange will need support.
I have never used Dragon Skin however so can't speak to the actual material. Since you would be working on the horizontal you may not need the thickening agent but you would have to try it to find out. I have used different silicones with thickening agents as well as added fillers for really large moulds, but I haven't made silicone moulds for a long time now so I am a little out of touch on the different brands available right now and their properties.
Block moulds are faster but use more material but if you are doing it for yourself and don't need to meet a deadline a brush on mould will save you on material.

[Kayakasaurus]

Block moulds are faster but use more material but if you are doing it for yourself and don't need to meet a deadline a brush on mould will save you on material.

Ok it looks like I'm going to go with the "dragon skin" and try skipping the hardner. Thank you for suggesting the brush on idea . I found a resin on Amazon that seems to be the least expensive. I plan to order two 16oz for a total of 32. This stuff hardens in under 10 mins, could you see that as being a problem? It has good reviews.

http://www.amazon.com/gp/aw/d/B0058V9KMK/ref=mp_s_a_1_2?qid=1427217352&sr=8-2&keywords=Casting+plastic&dpPl=1&dpID=5197b9xCuKL&ref=plSrch&pi=AC_SY200_QL40