Saturday, October 1, 2011

A mold making festivus! :D

Two part molds.. the next step to doing “pro” molding. I dove in finally & documented the process here! (Actually a bit of 2 stages - waste mold & then a production mold)... I do not promise this will be any kind of useful “tutorial”. I don’t explain things well, especially if I can’t sketch out things (well I could here but it would take me a while). Hopefully this will be of interest to some customers and maybe helpful to some artists too though.

This is what remains of the original clay after the 1 part first waste mold (first head on the left below). Then (middle) you see the first mold’s first casting in white there.. and then (to the right) in cold cast bronze the 2nd two part mold’s cold casting & final marble stand.

Ok, so before you write off the notion of a two part mold as being pretty basic and not good for casting much, consider this; my half passing thoroughbred sculpture “Deputed Duke” was a 2 part mold. No, I’m not kidding and I’ve seen and studied the mold with great fascination. It was breaking down so I had to throw it away when I moved (it weighed like 20lbs too).. but I wish I hadn’t tossed that one actually. As molds go? It’s brilliant (Will Rhodes of MVS made it, pretty sure I wouldn’t be able to work something like that out in my head personally). I’ve shown it to other mold makers and they have marveled over it. How can something so complicated be done in only 2 parts? ANYHOW, so the point I am making here though is these “waves” you see in the clay can really get crazy if you want and mold some very complex shapes. The mind boggles (well my simple mind does!). In rubber of course – for resin castings at least. The mold for Duke in fine bone china was 55 parts and was the “most complex mold” I heard that Mark Farmer of Alchemy Ceramics ever made (and one of his last). Very much unlike rubber, little undercuts are a bear – AND – for production you really have to think through what is going to grab and pull on your mold – even with the first casting!

Further confusing you I could add in that for things like the lost wax bronze method many are done as 1 part molds! The shell molding method.. I’ve done this too in college and … my clay is actually so soft I try to avoid the brush on methods. I’ve had this discussion with many sculptors & they’re surprised I love the super soft clay but I dunno… I just do. And yes, I accidentally bump it all the time & have to redo a nostril or ear or something key. I just don’t mind doing it over now & then. This is also why I am happily entrenched in dressage. I could ride along for years in a 20meter circle trying to get a few steps “just so” (mind you I love to cut loose full out breakneck gallops over stuff with horses too on cross country – LOW level stuff at least)… but anyhow, this is something I need to mention. So many people are used to this rock hard oil clay for sculpting. For me nope… onnnnnnly if I stick it in the fridge for a bit! ;)

When I molded the master/clay I wanted a 1 part mold.

(above) showing the narrowness - the waste mold box before I glued the end on (below) the box for the waste mold - ready to pour in rubber!

Well, truth be told I really wanted to have this bust just be a simple 1 part mold like I've shown above… in fact it’s simple enough that 1 part should be all I need EXCEPT that I planned on doing cold castings. If you google up cold casting videos and tutorials you’ll notice 1 common theme -> they all show open faced molds. There is a really good reason for this. The metal is heavy. It does NOT stay in suspension.

(above) I mocked up what a poured version of this resin would look like if I just mixed the metal in and poured it... the top of the horse would have all the metal settle out in the few minutes it takes for resin to cure. The metal mixed in with the resin is heavier than sand mixed into water.. so it settles VERY fast.

The end result here was that it was still hard to keep the metal in suspension, even following the open mold/brushing constantly method shown in videos.... I succeeded on a few times & wasted a lot of time & resin. In the end I went back to the pros. But I'm getting ahead of myself! ;)

So you can see from the trio above the clay.

Next was the white casting there from the waste mold. Steps for thatwaste molding for me was as follows;
  1. pour in rubber over clay (pray box doens't leak -- good news is that you can patch up leaks if you've got your hot glue handy... as me how I know this..) ;)
  2. wait a while (for Mold Star rubber it's not that long - 6-12hrs)...
  3. pull off sides and carefully cut out your clay casting - be sure to leave a totally uncut bottom.... really this is a 2 handed job without pause (so no pics) but there's great video stuff on Smooth On's site showing how to do this!
  4. dust in some baby powder & cast away! (see white horsie there in the middle)
Ok, sooooooo then you will note that the waste mold white horse there is lacking the bottom/tear drop sort of shape tie-in to the base. That took me another couple of weeks to get around to. I also added veining to the face and neck... filled in deep gaps in the mane.... basically all around made it into something "production ready" (& more mold friendly - too many undercuts tear up a mold). I'll confess too that when I started this bust last year I didn't really have a clear idea in mind of how I'd tie it onto the base so I was stuck with an armature that was immobile in that regard. Soooo when I finally had the idea in my head, my lil "vision" there finally, it was half a year before I could realize it after I made the resin "master" (the white copy used in the next sections below).

THEN, onto the "production mold" portion.

(above) Showing the basic clayed up production master sculpture. The line coming down from the chin is the "sprue" (sp?) I made out of a bamboo shishkabob skewer. The bigger sprue coming from the bottom of the neck I just made out of clay. Basically the overall goal here is to make your clay meet up to where ever you would like your seam to be. This is the part where you try to keep your seams off of highly detailed areas & tucked away out of sight as much as possible.

(above) same as before but I've added the acorn nut "keys". By putting these in at somewhat different angles I'm ensuring more "lock" will happen between both parts of the mold. I could've done an even better job of that - it was tricky to decide how much I wanted to. Knowing that I'd have to brush in resin, and THEN lock the 2 parts of the mold together for the pour later (a 2 stage resin filling method - outer shell of metallic resin & backfilled withplain black resin).

(above) ok, so this is after I've poured in the rubber & waited12hrs. I then do NOT pull off that rubber - I seal it even more with grease/oil/clay/what have you. I'm really careful here not to shift the master out of the mold rubber there though. That's one half of the rubber...

(above) this is how I did the bottom half. I now flip it over - cut off the bottom, being careful NOT to mess with the sides so the rubber stays nice & stuck sealed to them...and start pulling off the clay I've clayed him up with...

(above) I show how a little leak in the clay let some of that rubber in. I thought it was super solid too! Eeek! Sooooooo there I make a careful cut.. trying to think where I want that seam when all is said and done. (below) All done there.

(above) the acorn nuts removed, the mold greased up & ready to be poured into again...

(above) Now the mold rubber is heavily greased with some sort of mold release... I brushed it on.. I didn't want the horse to have one side more shiney than the other and I really don't like to use it much - detail loss!.. then I pour in the 2nd part of the mold.

(above) Literally next it just pops open & there you are. 2 parts to your mold. (below) Compare the mold to what comes out;

If only the story here was this simple! :D In reality I kept having a problem getting a nice firm cure from my resin. And it's a 20min process with the resin recommended (a clear amber colored resin) for the shell of these cold castings.

Here are the steps (again, not a camera friendly thing for me either here - waaaaaaay too messy!)...;

  1. Get the following out, plastic stirrer (spork!), rubber gloves, towels, and disposable brush (1/2" hardware store ones for under $1 hopefully). Remember that all of this will need to be chucked in the end so disposable everything...
  2. Lay out both parts of the mold side by side
  3. Get 3 small plastic cups out, and 1 large cup
  4. Pour out part B, add dye & mix
  5. Pour out a fraction of this in metal powder (I used less than recommended by Smooth On & it was more than I could manage/mix/blend)
  6. Mix this into part B when the dye is blended
  7. Pour out part A in equal volume to what part B WAS (remember to mark your cups if needed - the dye & metal added a lot to the volume so be careful!)
  8. Mix with spork (yaaaaay for sporks!!! spoon is good too but I just hoard sporks). ;)
  9. Now pour into the molds & start brushing up the sides/all over (see videos online on this - there are millions & it's worth watching). I was using Smooth on 326. I'm not loving it... takes 15min just about to start to gel
  10. Once starts to gel leave alone... start cleaning off any you might have gotten around the high sides of the mold that are supposed to be in contact with each other... clean out of spue areas for example
  11. Once it's not moving really at all - join the two sides. Press down plenty hard around the edges for 10min. Yes, it's easiest to just hold it in your hands & do this. Be sure to put mosquito repellent on before hand. I wound up getting resin on my body because I failed to remember that part of this step. ;)
  12. Put cardboard on either side, rubber band...
  13. DO NOT LOOK at your results. I made this mistake... you need to keep the two sides together & then backfill the inside here...
  14. DO however look inside while holding up to light (if you have uncured resin leaking out? that's wrongwrongwrong... & don't do this!).. you are looking to see if light is coming through your seams... you'll need to somehow fix that before moving on to the backfilling...
  15. Tilt whole thing up so the sprues are on top
  16. Mix new batch of resin normally & pour in like any other mold. Keep an eagle eye out for leakage since you're relying on a VERY tight mold. If you have a leak here your only recourse is to hold the two parts together for the duration of the cure... (get out yer bubble gum!)
  17. Demold and hope it all worked! :D
  18. repeat all of this a few times & you tell me if you aren't willing to pay a pro to do it properly at this point? HA!!! :D

Soooooo after 2 full days of trying to get a casting I got 2 decent ones but that's it. Annnnnnnnnnd it became clear that the casters equipment is better for the job! But here's the downfall to that. They use a more expensive/trickier mold rubber. Mine has tiny bubbles in the rubber. These turn around & make pimples.

MY castings - slow, not under pressure do NOT have very many pimples... (bronze above - see pimple pointed out by the arrow?). However for them to get good metal coverage they use pressure casting. I'm just not up for more equipment at this time - lol! I did my castings on plastic totes in the middle of my yard (best ventilation for my health - uncured resin, bad stuff!). ANYHOW, check out what pressure casting does on their first silver casting (below) for those hints of pimples! Eeek eh!?! I just used a couple of arrows to point out a few ... there are MILLIONS..!

Sooooooo after sharing all that with you I can safely say that this was mostly an exercise for me. HA! No, I will have the mold to try some other techniques and perhaps color ideas out on (like ...hmmm.. clear?). BUT the professional company I have had do my other cold castings (MVS) . It's expensive to make these to be honest. They weigh a bit so they use almost as much resin as some 1:9 scale sculptures practically! & Then after wards they are tricky to clean up well, and mount too... I haven't quite decided what to do here. I'll probably sell them as I have them available. Each being different. Aaaand offering a discount for show trophies since I've been asked about this.

So far the one from my last post & this fellow were all I've made successfully... there was a fabulous black/stainless steel one too but he's got more mane spots that didn't cure right... need to be removed & replaced (I just am using apoxie sculpt to fix these but they aren't "sale" worthy imo). Still, as hard as I am about it - not bad for a first try. The pouring/backfilling part is so crazy I can't believe it work at ALL! How funny that that isn't the part that's failing on me.... Maybe I'll find something better than this Smooth On 326 for me. I know the Smooth On 305 doesn't work at all for me here either... but 300 works better for me than I can believe! (Which is good news for those waste molds of my clay works).

So this is the end result;

Now you know what all this molding business is about (sorta). : :)