Questions About Latex (Sealing Clay and Adhesion)

Alexander H

Hiya folks! I'm finally gonna dip into learning latex skinning techniques - I've put it off for too long since I don't really have the workspace for the mess, but somehow, I'll make it work.

I've watched a few courses here on molding/casting latex so I've got some idea of what I'm doing - I'll learn more as I make mistakes - but I'm wanting some extra help before I get started.

Firstly, from what I remember, people seal their clays before making the plaster molds, to protect the surface of the clay and make it easier to demold later. I've got a tub of Monster Clay I was hoping to use to sculpt the creature, but I don't want to have to throw that clay out if I have to add contaminants to it. Is there a way to create the mold without sealing it? The mold wall for the flange is also a concern. If it is best to seal it, what's a decent sculpting clay that isn't too painful on the budget, that I could toss out afterwards?

If for some reason I need to glue latex to itself, does it adhere to itself (with some fresh latex as a glue) or will I need an adhesive like Pros-Aide? And if I needed to glue the latex to plastic (such as PETG or PLA), is Pros-Aide good for that too?

Troy Mccombs

TBH, I don't seal my clay before I mold in ultracal. I just spray it with furniture polish to prevent the plaster from beading when I apply the detail coat.  I have ALWAYS had trouble with 2 part molds, getting the front half off the armature. But last time, I think I figured it out. Put the dividing wall on while the sculpture is upright, and mold the BACK half first. Once you've got the back half molded, take the clay wall off, vasline it, add clay pry points, and mold the front half. The trick is this: you want to demold while the plaster is still warm (but still as hard as it can be; if it's crumbly, it's still too early, and if you can scrape the plaster off easily with a fingernail, it's still too early). The warmth will help with demolding, making the front easier to remove.

Alexander H

Thanks for the advice! I'll need that extra reminder to add pry points because I'm sure I'll forget and learn the hard way. Great tip about when to demold the plaster too.

The while the furniture polish may not exactly be a sealant, it's still a foreign material to the clay that I worry will mean the clay will be useless afterwards. Do you just throw out the clay afterwards? If so, what clay do you use?

James Shaver

If you are using Monster Clay..no need to seal... and when demolded..simply put the clay into a crock pot..melt it down..
stir..and pour back into the container

Troy Mccombs

I use monster makers monster clay, soft, and the furniture polish doesn't hurt it. For most sfx artists, I think the only throwaway clay is the WED or pretty much any water based clay. Anything with oil you can use pretty much forever.

Alexander H

If you are using Monster Clay..no need to seal...

@James Shaver When you're adding the mold wall to the sculpt to make the flange, how do you prevent the clay from sticking to the sculpt and messing up the details?

I use monster makers monster clay, soft, and the furniture polish doesn't hurt it.

@Troy Mccombs So the additives (furniture polish) mixed into the clay now don't mess up the clay at all, and you can keep reusing it?

Sorry guys if I'm re-iterating some stuff, I just want to make sure I'm on the same page as you before getting into all of this. I really appreciate the advice!

Troy Mccombs

Wet clay (for wall) doesn't really stick to oil clay very well. I've never had a problem getting it apart from the sculpture. And no, furniture polish won't hurt the monster clay. You can reuse it forever. The furniture polish breaks the surface tension of the clay so that the plaster top coat doesn't bead off when you're brushing it on

Chris Ellerby

Usually, the clay for the walls is softer than the clay used in the sculpture and has a different formula, so the two do not want to merge.

Also, when you melt the clay and mix it all back up after you are done with a sculpt, any surface coating makes up such a small percent of the total volume that it does not really impact the quality of the clay in any meaningful way.  

/Chris

James Shaver

@Alexander H I primarily use playing cards for my molding...but this is a fiberglass molding

James Shaver

@Alexander H when i do a latex version i use the clay walls BUT i lay the sculpt down and make the walls "cupped" upwards in a ring around the outside so i can pour the Ultracal into it ( reinforcing it with wood blocks underneath)

Tom Luca

Not sure if anyone posted this yet but this is just one of the supplies we purchase/buy and use for sealing clay prior to molding. The industry is constantly innovative and discovering other wats or techniques to work but we usually stick with what's best and works. But our R&D Department does coordinate with the shop to see what is on the market that can be better and less costly.

Tom Luca

And yes, Latex does stick to Latex but you can use Pros-Aide too. For PETG / PLA I'm not sure because we do not 3D Print only traditional by hand sculpting, building, fabrication, etc. 

Alexander H

Thank you very much for the advice everyone!

I've got some Rustoleum clear coats, so I'll be able to use that when I'm ready to cast. Unfortunately, I don't seem to be able to find any water based clays easily available - I can get WED clay from Barnes, where I'll be getting my other plaster/latex supplies from, but I worry that it's a fair amount of money to spend on something I only need a little of, and aside from that I don't have room to store that amount of clay, I worry it may dry out before I get to use it again.

So, I wonder - what about air dry clays, like this? Or even Play-doh? I was thinking foam clay, but that wouldn't sculpt well enough to produce a nice flat seam line.

Edit: Reading in a couple of places that Play-doh contains Aluminium Sulfate, so that would be a no-go to avoid contaminating the clay I would want to use with silicone in the future. Perhaps Sculpey clay, or Chavant?