Moldmaking.. how to? (step by step)

[FinnishSpartan]

Okay, After doing alot of reasearch... wathing hours of videos... i came to a conclusion on how i will mold my helmet.
I just want to check if my plan would work out and if i need to change anything...

I think my technique should be just about right, and could be used by others.

My plan: (after finishing my mold)

Silicone detail.
-Mix silicone rubber, apply thin layer of silicone with a brush for detail.
-add 4-6 layers more with a brush (letting each layer cure until it's "tacky").
-Create keyes (parting lines) using thickened silicone.
-add layer(s) of silicone.
-Let silicone fully cure.

Mother mold. (2 parts)
-Create a ridge using clay to seperate 2 parts
-apply release agent. (any suggestions please?)
-Add plaster bandages to the 1st side of the mold.
-Let plaster fully dry.
-Take off clay.
-add release agent (cant find vaseline... any ideas?)
-Add plaster bandages to 2nd side.
-let it fully dry
-use a chisel and a hammer to seperate 2 part plaster mold from each other.

Preparing for casting.
-Pull mother mold from silicone.
-cut a line trough the "keye" areas, to "open" the silicone mold.
-Pull original model from the silicone.
-"insert" the silicone mold into the mother mold.
-Mix small amount of polyurethene resin.
-Pour it in to the silicone mold and slush it around.
-Repeat previous step as many times as necessary.
-wait for it to fully cure.
-Pry open your mother mold and silicone mold.
-Take your cast helmet.

Party.
-You finished your helmet cast! It's time to celebrate your hard work!!!!!! Yay!!!


I just want to check if this is right. If it is... I'm happy if others use it too

-Finish

EDIT: i will add pics and videos as i get working on this.

 

[Nicktendo]

Looks pretty routine, from what I can gather. One thing though...

Mother mold. (2 parts)
-Create a ridge using clay to seperate 2 parts
-apply release agent. (any suggestions please?)
...
-use a chisel and a hammer to seperate 2 part plaster mold from each other.

I don't know if clay is necessary. Then again I don't really know what you're getting at... Reference pics? Also, I don't think you should have to resort to a hammer and chisel to get the mother mold apart. That's why you use a release agent (btw, 'Petroleum Jelly' is, I think, another name for Vaseline) and do the two parts separate. (One half dries before the other side is started) They shouldn't be given the opportunity to join, really.

EDIT: NVM, I see what you're doing with the clay. This is a good tut with example pics...
http://www.sculpt.com/technotes/2_piece_mold/1_intro.htm
They do their process a little differently, doing one whole side at a time (silicone, mother mold, then the other side) but the main idea is the same.

EDIT EDIT: Holt cow... That main site is a mold making gold mine!
http://www.sculpt.com/onlinetech.html
That right there should be a mandatory read.

EDIT EDIT EDIT: I'm having a field day here! Step-by-step video by Smooth-On here.

 

[falcon NL]

Why would you use Adams ODST method ? And if you are planning to make a two part jacked..why not 2 part mold ?

 

[FinnishSpartan]

Why would you use Adams ODST method ? And if you are planning to make a two part jacked..why not 2 part mold ?

The mother mold has to alway be atleast 2 parts... otherwise you cannot seperate it from each other...
The silicone can just be peeled off...

I have been thinking about a 2 part mold... but you do that by pouring the silicone usually... wich takes alot more silicone to work with (aka. more expensive)... I'm not sure if you can 2 part brush-on mold.

And no i'm not just copying adams video...

-Finish

EDIT: Nicktendo: plaster bonds... even if the other side is dry.

 

[falcon NL]

The mother mold has to alway be atleast 2 parts... otherwise you cannot seperate it from each other...
The silicone can just be peeled off...

I have been thinking about a 2 part mold... but you do that by pouring the silicone usually... wich takes alot more silicone to work with (aka. more expensive)... I'm not sure if you can 2 part brush-on mold.

And no i'm not just copying adams video...

-Finish

EDIT: Nicktendo: plaster bonds... even if the other side is dry.

I was meaning, if you take the afford to build up a wall why not do a 2 part mold? And yes u can brush on a 2 part mold... it more commonly used for this sort of thing.

http://405th.com/forums/index.php?showtopic=4781 <-- maybe a thought if your not sure how to make a 2 part brush-on mold...

 

[Nicktendo]

I have been thinking about a 2 part mold... but you do that by pouring the silicone usually... wich takes alot more silicone to work with (aka. more expensive)... I'm not sure if you can 2 part brush-on mold.

EDIT: Nicktendo: plaster bonds... even if the other side is dry.

Yeah you can. The link I posted shows it. It seems like it would work just fine along with good keys and registration.

And the vasoline/petroleum jelly should keep the plaster separate. Separate enough anyway.

 

[FinnishSpartan]

Yeah you can. The link I posted shows it. It seems like it would work just fine along with good keys and registration.

And the vasoline/petroleum jelly should keep the plaster separate. Separate enough anyway.

Oh, you mean that type of a mold... The only problem with it is that it's quite difficult to keep the part's together (since plaster is difficult to drill etc.)

-Finish

 

[Nicktendo]

Oh, you mean that type of a mold... The only problem with it is that it's quite difficult to keep the part's together (since plaster is difficult to drill etc.)

-Finish

Well, drilling is only one of your options. Bands or straps are also commonly used. As long as it stays together, lined up with the registration, you should be fine.

To make mine more lightweight and the casting process easier, I thought I'd do my mother mold (if i ever get to that point) in fiberglass instead of plaster. Plaster gets damn heavy, and for slush casting, that'd be a pain.

 

[FinnishSpartan]

Well, drilling is only one of your options. Bands or straps are also commonly used. As long as it stays together, lined up with the registration, you should be fine.

To make mine more lightweight and the casting process easier, I thought I'd do my mother mold (if i ever get to that point) in fiberglass instead of plaster. Plaster gets damn heavy, and for slush casting, that'd be a pain.

I'm going to use plaster bandages... it shouldnt weigh more then 4lb's when it's finished.

-Finish

 

[Nicktendo]

I'm going to use plaster bandages... it shouldnt weigh more then 4lb's when it's finished.

-Finish

Ah, yeah, I suppose that would add strength without much mass. The mother molds I've seen around in the sculpture lab at my university are completely plaster, no bandages. I don't really know what it's like with bandages.

MAN I am anxious to get working on my build... School needs to end already.