Mold Making Experts....got a question for ya

Ive done about a dozen or so molds, jackets etc. I make them at least 1/8 to 1/4 depending on the project. But after watching the EP3 vader video (in the new DVDs) I started wondering how they made what appear to be little teeth or crenelations which I presume were designed to lock down the mold, ie, keep it from flush up against the edge of the jacket....ie, to prevent the mold wall from pulling away from the jacket wall.

Ive used clay as a non stick guide into which Ive poured a freshly mixed liquid mold.....and partially used it on a still drying but gelled layer to guilde the next layer... but I must admit I am unsure how locking plugs or stems like those crenelations around the EP3 Vader mold were made. Only good method Ive found to keep the mold firm against the jacket are small strips of foil tape which have a clamping affect-- and its fast/easy to use.


What do you mold gurus do to keep your mold against the jacket?

How the heck did they make those crenelated teeth on the leading edge of the EP3 dome?

Are these cren-teeth likely designed to as a means to secure the mold against the jacket?

 

I'm sorry to not know much about moldmaking here, Drew, but your question (and the quality of your work that I've received in the past.) compells me to ask my own question of you:

Do you have a good mold or master to make a dome part of a vader ROTJ helmet? I am building up a reveal, but don't have the outer helmet. Let me know if you have a good ESB/ROTJ shell. I've contacted Portumac about his, but I'd love to explore as many avenues as possible. Thanks for your time.

-Douglas

 

Those are sculpted in clay (over the model) and the outside jacket is made first, then that clay is removed and the silicone is poured, filling the jacket and covering the piece being molded.

Another way of saying it is that what "will" be silicone, must first be made in clay including positives for the jacket to be made over (fiberglass or stone).

Make sense?

 

Great question.

I´m having the same problem with some molds I´d like to make of custom sculpted armor parts (for a Luke imp. guard costume).

I don´t cover the master with clay, make the shell, remove the clay from the master and pour silicone in the mother mold, but did a mold with brushable silicone. Then I made a mother mold out of plaster, but after removing my original sculpt, I had problems with the silicone not laying flush to the shell.

Result: the surface of the cast was bumpy :cry

So the question is...how to use brushable silicone and having it "stick" to the shell?

Markus

 

One solution if you don't use the method mentioned above is to cut up old t-shirts and lay them onto your final layer of silicone.

This takes a lot of patience to get it just right, but if done correctly, you can do the mothermold in fiberglass because the cloth adheres to the silicone on one side and fiberglass on the other.

 

Here is another mold technique.

Ever wonder what to do with those RUBBER DISCS you keep collecting?
You know the UN USED SILICONE that gets wasted in the BUCKET?

Well, DONT throw em away.

Look here:



Take a Brass tube and Sharpen the edge.
Now over some wood, PUNCH out holes in the RUBBER.
Take the "HOLES" and look at em. Notice the HOUR GLASS SHAPE?
Ok MAKE a BUTT LOAD OF EM.

Lets call em KEY PLUGS

Hmm....what to do with them. Ok..next time you PAINT on your silicone, which by the way you can make ANY SIlicone BRUSHABLE by adding a thickener,.....take a KEY PLUG and set it on the SILICONE. Not too Deep, just enough so it adheres.

Place them about 2 to 3 inches apart OR closer or FURTHER depending on your piece.

Note: You MIGHT want to make a THICKER Skin. If your Silicone is gonna SAG between KEY PLUGS then YOU ARE MAKING YOUR SILICONE JACKET TOO THIN.

1/8 or 1/4 could work for SOME parts....but that seems awfully thin.

(The SILICONE NEEDS TO HAVE SOME SORT OF STRUCTURAL INTEGRITY.
Mother jackets help us use LESS Silicone...but..not THAT much less..)

Silicone LOVES to STICK to silicone as many of you know who accidentily made a ONE part when you were trying to make a TWO part mold.
DOH..

Anyways...Once rubber sets up. Paint FIBERGLASS MUD around the little KEY PLUG
and make sure its covered. Now Fiberglass over the rest of the silicone.

When it Dries, Your Silicone will STAY very close to your fiberglass.
It will pull out when you want it too...and LOCK back in when you want to return it to the jacket.

Make sense?

Frank

 

Great idea Frank

I thought about using silicone covered wooden "plugs" already...
Problem was, that the wooden bits kept "sliding" down on my curfed surface :rolleyes

Markus

 

Careful.......Wood doesnt FLEX very well

You can also let the SILICONE DRY....when youre ready to glue the KEYS on....mix some more silicone in a cup, over kick it a bit...and GLUE the KEYS on.

Works great.
You can also use Denatured Alcohol to brush over your silicone to SMOOTH it out.
You want it as smooth as possible, and KEYED well.

 

Great thread gents.


I typically use polytek 71-20 which I like but it wont stick to itself once dry...ie, a dry layer wont stick to a wet one or vice versa.....so a plug wouldnt stick.

Sporkak....this does make sense. Remind me to kick myself for not thinking of this earlier.

Frank, what kind of molding material do you use.

Of note, I have found that taking the semi-gelled globs and criss-crossing the in progress still wet mold adds moutain and valley texture to the rubber mold, making for a sort of key/keyhole grip system.

My fundamental problem on some probjects, not all, but some....is when the edge per gravity's annoying tendency, slouches over. Foil tape is rigid and will hold but it must be applied very carefully so it doesnt extend over into the actual mold.


Again, this is one of those types of threads that should be archived....the info is excellant, even with a half dozen posts.



Hey, that brings up a good point....we should start a "Techniques Forum" .....for technical and logicstical approaches to projects. *, thats a good idea.




.

 

I've used polygrip to hold alginate molds in place around the edges temporarily. It might work for other materials as well.

 

ewwwwwww
Rubber that wont stick to itself.

Could be usefull for two part molds.

I used SILPAK 1628. Great stuff. I have a distributor close so I can just drive over and pick it up.

Frank

 

Here is a set of Photos from a DVD available showing the process of making a Silicone mold with a Plaster Jacket:







Here is the end result:



Here is a link to the DVD:
http://www.thegnomonworkshop.com/dvds/scu04.html

His name is John Brown and he does great work:

 

Thanks so far guys...

But I still have a question.
I you make a plaster shell by covering the master with clay, how in the world do you ensure that the silicone will cover the complete surface of the sculpt with no air pockets/ bubbles?
You have jus one pour spot at the top of the shell while I´m used to pour the silicone into the lowest spot of a mold, letting it seek its own way.

Know what I mean? It just looks to easy.

Oh...what if the master is made of clay and you´re building up a layer of clay before adding the shell? How do you prevent from sticking it to the master?

Markus

 

"I you make a plaster shell by covering the master with clay, how in the world do you ensure that the silicone will cover the complete surface of the sculpt with no air pockets/ bubbles?"


Gravity.
Once the Plaster is dry, the clay is removed and the HOLES (screw size) are drilled into the plaster to insure all AIR will escape. Any HIGH point in the CLAY is gonna catch air when its "Rubber". The plaster is placed back over the master, sealed (hot glue) and the Silicone is poured in as the MOLD FILLS and AIR leaves...eventually...Silicone LEAKS out of the AIR holes you made. Take a wood or dry wall screw and PLUG the AIR HOLE.


"Oh...what if the master is made of clay and you´re building up a layer of clay before adding the shell? How do you prevent from sticking it to the master?"

Suran wrap covering the master works.
Im not sure how you keep from DAMAGING the master. I have never had a CLAY master, so I defer to those who have done it with one.

Frank

 

Be * careful with plaster of paris (if thats what you meant) as the weight can distort your original and the silcone covering it.

Ive had this happend with some authentic Medieval helmet molds/casts Im working on...the original plaster of paris mother mold halves (layered on thick enough to be strong, ie, at least an inch) squashed the helmets (not permanently) but enough so that the shape and form which is heavily determined by the jacket mold was distorted.....I have thus started using fiberglass mother molds as they are much lighter and superior in strengthr....and wont break if they fall either. Granted more expensive but worth it for all those other advantages.

 

I also prefer Fiberglass Shell Molds because of the Weight Factor, it's much easier
to work with because you won't have a 50+ lb Shell over the silicone.