Joining platinum silicone?

I will have pieces need to be seamed/joined together soon (arm to torso, leg to hip, etc.) I know platinum like to stick to itself, could I just mix some Ecoflex 30 and seam the two pieces with that? The join pieces won't be under much stress or moving, just afraid of it delaminating. Does anyone have experience or tips for this?


  • Options
    Todd WatsonTodd Watson ✭✭
    edited June 2017
    Hey Blake,
    Smooth-On makes a great glue called Sil-Poxy for just this purpose. It's semi-clear and sets in about fifteen minutes. However, it's pretty pricey and will set up in the tube if you don't keep the cap on, be warned! There's another silicone adhesive, Shin Etsu, which is cheaper and also semi-clear, but the set time is MUCH longer, hours, so if you have more time than money (or just need the working time), it may be the way to go. It also comes in a caulking gun size if you need lots of coverage without breaking the budget. Here's a link to both:


    Also, I've worked plenty with eco-flex, and as it leaches softener/deadener after casting, make sure to clean your surfaces well with acetone IMMEDIATELY before gluing to get the best bond.
    Hope that helps! 
  • Options
    Blake BradleyBlake Bradley ✭✭
    edited June 2017
    Thanks @Todd Watson I'll look into both. In your experience will the sil-proxy or Shin Etsu bound to the Ecoflex after the 72 hour window? I'll be casting bigger piece and then making the animatronics. I'd like to just cast once on some piece, which may result in a few days before seaming.
    Also, any cheap paint mix for the Ecoflex? And what do you clean it with before painting. Thanks in advance.
  • Options
    Todd WatsonTodd Watson ✭✭
    edited July 2017
    Hey Blake, sorry for the slow reply, on vay cay. Our shop made two eco-30 masks for Netherworld in Atl. last summer and the castings for the various pieces were made a week apart and went together without an issue using sil-poxy, in our heat and humidity! They had multiple tentacles and webbing, and even with nightly use for the whole haunt season, the silicone would give before the bond would, so no worries there. Ditto for shin etsu, we glued dragon skin elements to a polyfoam body and it was in the OCEAN for hours the next day and held up perfectly.

    Just make sure you really scrub your pieces with acetone or naphtha RIGHT before bonding. I use a cut down chip brush and work top to bottom, making sure to get in every fold release may hide in. Repeat until you feel you've gotten every bit of gunk off. Don't rush this step, your paint adhesion depends on it.

    There are a few way
    s to skin the paint cat for platinum silicone.
    The first is psycho paint, again from smooth-on. You can tint it with art store oil paints, or their silicone friendly silc-pig. Thin with naphtha to make a wash or get thru an airbrush. On the upside, even trial kits of those should be enough for painting a fairly large project once it's thinned. And a little silc pig goes a loooong way. On the down side, neither are cheap, and once opened, psycho paint has a lifespan. It's a pretty long one, but be aware.

    There's also fuse fx, incredibly useful premixed colors for fx painting that cure quickly, but again, pretty pricey and they only recommend a two day casting to paint time.

    The third method, I haven't tried (but will!).  There's an article in Neill Gorton's excellent magazine, Prosthetics, about Frank Ippolito painting eco-20 with oil paints mixed with smooth-on's NOVOCs-thinned sil poxy. It would save buying the pp and sp, and the cure time is minutes instead of hours without heat. The caveat here is if you've got to cover lots of area, sil poxy and NOVOCs ain't cheap either!

    Careful with handling while you paint, too. Until the paint/silicone mix sets it's like any other wet paint. You can force cure with a blow dryer or low heat gun, but it may yellow your finish if you hit it too hard, so easy does it.

    Just a safety note here too, my friend. Acetone and naphtha are CRAZY bad for your health, so make sure you work in a well ventilated space and wear a real respirator and gloves when doing your cleaning, gluing and mixing paints, and use fans when you paint.

    Good luck! 
  • Options
    @Todd Watson Wow! Thanks for all the handy info! Hope you had a good Vakay. I called smooth on the other day and asked about these types of things, they said ( in essence ) the same as you. How ever I did ask if I could just mix Eco with ThinVex and use it as a binder and they said yes, have you had any experience with this? 
  • Options
    Yeah, Blake, CONCEPTUALLY you can use more of what you made your pieces with to bond them together in most cases, but I haven't tried it personally with Eco-Flex. However, it's so naturally thin, it would be a big mess as it squeezed out of the joins during assembly, and full bonding time will be hours instead of minutes.

    I have used Thi-vex to thicken rebound 40 and dragon skin to build up thickness for brush-in layers, but the softener/deadener that makes Eco Flex so pliable is the opposite of what Thi-vex does, and you run the risk of having it not set up entirely, then you have a REAL mess.

    We had that issue earlier this year on a project that required a body with lifelike skin cutting properties, we decided eco would reseal well for retakes, and have a stretchy quality for peeling back the skin as needed. We did several beauty coats in the mold with Eco-20, then started adding Thi-vex to it to build thickness layers. It held the verticals well, but would never set completely, staying in a heavy gel state even with days of time and heat curing. VERY luckily, were able to get it to seal over with a few more layers of unThi-Vexed Eco, but we nearly had to start the whole body cast again, a BIG waste of material and time as the deadline approached.

    sonally, I'd use sil poxy for my joins, and clean up my seams with more eco, or psycho paint tinted to the same shade as the cast pieces. Just set aside some of your casting material from the original parts, and go easy on the Thi-vex you seam with, testing your ratios to make sure it will cure entirely before using it on your hero piece.

    Also, unless you have an extreme range of motion in your animatronic, dragon skin is a LOT more stable with thinners and thickeners, leaches less oil over time, and paints, glues and holds punched hair like a dream. Just sayin'! ;-D

Sign In or Register to comment.