Molding Q&A

Hi! 

First let me start off by saying my posting time will be painfully slim for a little bit - as I'm still trying to get caught up and set back-up after hurricane angst.  I also feel pretty badly for anyone out there to the north that's getting it much worse than we did.

So, without further furtherness...

Q#1) There are many ways to construct the standard 2-part mold, the most tradtional route would feature keyholes or jagged angle cuts to make sure the two mold halves marry together firmly (that would usually require pouring the two halves in seperate batches, where one was poured against a clay wall with air-vent and pour channels already sculpted in, along with studs or ridges that the second mold half would form against when the clay is removed, to help everything lock in place.)  There's also a method called matrix molding, which is a complicated affair that involves doing the same thing as above but first wrapping the item in clay, making a plaster outer mold and then removing the clay and filling the empty space with silicone...  Honestly in my experience it isn't really a better technique, and is a little like molding a pea inside a coconut through a straw hole - quite fancy and unneeded. 

SO - Yes, just reconstruct a lego box.  I build four walls that overlap but don't interconnect -they  are all secured to the same baseplate, and then locked together with bricks at the top.  This will allow you to put up three of the four walls, shimmy in the mold and readjust it to make sure it's aligned properly before adding the last wall.  If you're looking for a little extra help with alignment, you can also cut the mold off-center.  If you were to look down from the top of a head or helmet then you'd be cutting the mold halves apart in a V shape.  So that one half nestles a bit inside the recess of the other.  Just remember it's best to make the mold seperation on an area that's a detail edge, say the termination of a face plate or some other ridge feature, so that any mold lines you do have will be less noticeable (as opposed to a smooth surface with a more noticeable line) sometimes this can't be helped though, as stormie helmets have dome tops.   alos Micromark offers a different silicone mixture which is a little more expensive but cures transparently instead of colored as the standard does.  When using that it's easier to see exactly where you're cutting the mold apart on the original.  I don't use it myself, but it might be usefull for someone just getting into it if they're a little unsure of where the blade is going.

Q#2) The more rigid silicones will stay true to form better, the more flexible ones will be less likely to break in thin sections as well as flex a bit better whenremoving casts if they're made "wrapped around" certain features ...  So basically it depends on what you want to do.  Either extreme will be less rugged for long term use for different reasons.   My general suggestion would be shoot for the middle and go with what you've described as a #2 silicone.  The micromark brand I use is probably closest to a #2, with a little give and fairly good strength.  for really, really delicate molds (that have a lot of recess or deep undercut or keyhole sections in which a molded part might actually be slightly larger than the hole in the mold that you're pulling it out of) I'd suggest a stronger mold silicone, or, you can buy additives that will increase the tensile strength of the silicone to both extend the mold life and also allow you to pour it in thinner sections.  As an example, say you made a mold of a clormie helm with just a blank minifig head shape as the interior, and the T shaped eye cut out as part of the front piece of the mold.  As you take multiple castings, over time the silicone will stress from the plastic being pulled off of it, and either it will lose little bits of material on the edges as the plastic is pulled away, or larger parts will break off the mold and stay with the helmet as they're seperated.  In either case it'd be time to retire the mold and make a fresh one - but strengtheners will extend the mold's life.

-Robert

"The problem with LEGO is that you can't eat them - or at least it's very painful."

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"The problem with LEGO is that you can't eat them - or at least it's very painful."

Thanks for the info Robert, here's few new questions:

Question #4: I have been dusting my molds with baby powder before casting, and it seems to be working to help pull the resin up into the hard to fill areas.  Do you use this method?  Have you used it?  If so, to what results?

Question #5:  The casting instructions that come with the resin say to heat up the molds.  I've been sticking them in the microwave for 1 minute, then letting them cool for about 45 seconds while I mix the resin elements.  Do you also heat up the molds?  For how long?  I know it makes the resin set faster (which can be bad) and I have had some bad results when it was too hot.  Your own poinions on heating the mold would be helpful.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

#4)  I have used a dust mold release in the past (as well as a spray form marketed under the brand Air-Rid, which is mostly designed for plaster casting but is also plastic worthy).  Both work well (and there's an industrial talcum available from Micromark which is a finer grind than babypowder, but I haven't compared them hands on).  The only drawback to use is that it may ever so slightly change the surface texture of your cast.  You can cast directly from plastic on silicone without a release agent, but as you guessed it does ever so slightly increase odds of bubble formation.  The best route is experimentation since you never really know what will happen ahead of time.  As a matter of fact, I don't cut air flow channels until after one test cast - this will show you where air "actually" groups in your mold... plenty of times I've been sure X space will be a problem only to find out it's smooth and fully formed during casting - that will cut down on the number of unneeded sprue marks on your finished item.

#5)  Uhm... Hmm.  See here's the thing - What heating them does is supercharge the chemical reaction in the plastic.   because of it's temperature exchange properties heat will hang around in silicone for a long time (that's why it's such a good window insulation - it's adverse to temp change).  You'll notice if you pop a mold, extract the pull and cast another in a short time, the plastic will set-up faster in the second casting than the first because the mold retains heat from the first cast.  This isn't always a good thing.   If you're having bubble problems, or if you've made a bottom feeding mold (a type in which a giant J shaped funnel is your pour entry, that then feeds plastic to the casting hollow from the bottom-up) than a way to keep the plastic mix from setting up as quickly (and thus extending the liquid-pour time) is to actually refrigerate it.  You can refrigerate your plastics, your molds or both.  A few things to remember is even is a mix claims low or zero toxicity - never store it near any surface that shares food or food prep.  Also, you want to keep your plastic mixes very very dry, as any moisture at all will increase "foaming" in the plastic mix when it heats creating brittle end plastic with lots of bubbles.  the heating is not needed for set-up, it simply hastens the process.  I personally don't heat the plastics or molds, but then again I use a quick 15 minute set plastic, not the multi-hour types that are also available.

 To combat moisture make sure they're sealed tightly, also you can purchase heavy gas cans which work like pressurized air (as you'd use on your keyboard) but are filled with inert, heavier than oxygen gas that fills the mix bottle to the lid, keeping out any ambient "air" that might carry moisture with it.  These can extend the life of unused plastic by about six months, but you have to refill the bottles with gas every time you use them for it to be very effective.  If you're using the plastic quickly (which is better since it has a shelf life) you probably needn't worry about getting supplies like that.

-R

"The problem with LEGO is that you can't eat them - or at least it's very painful."

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"The problem with LEGO is that you can't eat them - or at least it's very painful."

Hey Recluce, I hope you don't mind me hijacking your forum a bit and asking a question to Tothiro... [b]Question #6:[/b] Hi Robert, I was wondering, when molding custom accessories (flat ones like tools, guns ect) do you use the same techniques as when molding helmets? If not, could you tell me how you manage to avoid air bubbles? ~ [i]Victor[/i] ...and don't expect me to change that avatar! 8) [url]http://www.mocpages.com/home.php/1256[/url] [url]http://www.brickshelf.com/cgi-bin/gallery.cgi?m=Supercat7[/URL]

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- Unknown Artist, Moderator of MCN

Unknown Artist Studio | MOCpages | B-Shelf

Of course I don't mind, this is a forum for all to post questions.  I'll give my own answer to your question, but of course Tothiro may have a better one.

#6 I have yet to mold a flat item, but I can tell you how I get the air bubbles out:  I tap the mold against a table.  After pouring the resin in, just tap the bottom of the mold against the table until the air bubbles start to move to the top.  If necessary, add more resin.  Then just keep tapping until there are no more bubbles or the resin has started setting.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

 [b]Question #6:[/b] Hi Robert, I was wondering, when molding custom accessories (flat ones like tools, guns ect) do you use the same techniques as when molding helmets? If not, could you tell me how you manage to avoid air bubbles?

(answer:) Small items are tough in resin precisely because of air bubbles... That's one of many areas injection plastic has a firm upper hand.  There are things you can do to close the gap, though.  As Recluce suggested you can tap the mold if you're using a slower-set resin that stays fluid for longer periods.  Another thing to consider is the angle of your mold.  If you're casting a relatively straightforward shape (baseball bat) you'll want to mold it with as vertical an orientation as possible to allow air to flow upwards.  If you're casting a more complex shape (candlestick) you may mold it with a slight degree tilt, so that when the air flows "up" it's actually moving diagonally relative to the item you're casting (going to the sides of the wider candlestick features) - then you can cut air escape channels off of the most air-grabbing features of the piece.  Just remember you're trying to herd all the air as quickly and smoothly as possible out of your part - and that's always up.  The third consideration is also a mold set-up concern.  When making your mold you'll want to consider if the piece will cast best by pouring resin in from the top and allowing air to escape on the sides, or if you should set it up as a bottom fed mold.  Bottom fed molds usually do a better job of getting the bubbles out if the air channels vent well... the material will pour into a funnel that goes down into the mold, out a relatively smaller opening at the base of the part you're trying to cast, and then flow upward filling to fill the cavity while being pushed by the weight of the additional resin pouring in behind it.  As a general rule though - without pressure pots or vacuum chambers you will always have to deal with bubbles.  In resin bubbles occur both because air has been mixed into the material from stirring, and because gasses are produced and released during the chemical reaction.  So no matter how gently you stir there will be small bubbles throughout the material but you don't see them because they tend to gravitate away from the outer surface (it's a science thing - the same way water forms a "skin"...  bubbles want to stay round from equal distribution of pressure in all directions, so they won't stick to flat mold walls as much).
Really, really narrow areas (Solo's blaster barrel) are the most troublesome because they're so tiny that any bubble at all will significantly weaken the structural strength of the plastic because it just takes up so much space.  If you've got a really narrow bit that's giving you trouble you might consider alternate construction methods (like a stock bit of plastic with elements that can be cast and attached - A cast sword blade that accepts a lego screwdriver element for a handle if making a Cloud Strife custom for instance).

-Robert

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"The problem with LEGO is that you can't eat them - or at least it's very painful."

Thank you very much, Recluce and Tothiro! I'll try first tapping the mold and then changing the angle of the mold the moment I get the next party of molding materials... ~ [i]Victor[/i] ...and don't expect me to change that avatar! 8) [url]http://www.mocpages.com/home.php/1256[/url] [url]http://www.brickshelf.com/cgi-bin/gallery.cgi?m=Supercat7[/URL]

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- Unknown Artist, Moderator of MCN

Unknown Artist Studio | MOCpages | B-Shelf

Hey I have a niave question, couldn't you throw your mold in a big plastic bag and add your plastic.  Then take a vacuum cleaner and using the hose attachment vacuum the air out of the bag/mold.  If necessary then add a bit more plastic to the mold and vacuum again.  I figure this will remove most of the air bubbles and be a cheap vacuum option.

Jared

Jared "Kaminoan" Burks
Kaminoan's Fine Clonier
www.FineClonier.com
FineClonier@gmail.com

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Kaminoan
Kaminoan's Fine Clonier
www.FineClonier.com
FineClonier@gmail.com

wow, Kam, I never thought of using vacuum cleaners... I should try that one, too... Though changing angles of the mold has worked OK for me so far...

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- Unknown Artist, Moderator of MCN

Unknown Artist Studio | MOCpages | B-Shelf

The problem is that the resin sets up very quickly, in about 1 minute for the black, and 2-3 for the white.  That leaves little time to do the ole switcheroo.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

Get a big bag and add the plastic to the mold inside the bag with one hand, while the other holds the vacuum hose.  Show it in as you remove your hand and suck out the air.  Just a thought.

Jared

Jared "Kaminoan" Burks
Kaminoan's Fine Clonier
www.FineClonier.com
FineClonier@gmail.com

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Kaminoan
Kaminoan's Fine Clonier
www.FineClonier.com
FineClonier@gmail.com

I just want to know 1:how do you make your own molds?
2: How do you make somthing like a helmet or a head?
3: whats the best plastick to use?

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The forums: http://z3.invisionfree.com/Fantasy_Bricks/index.

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~Crazy Boy / Ollie  
Brickshelf | Flickr

Oh also is it posible to cast mini fig parts so I can create my own? I want to make some purple ones so I acn create the night elfs from warcraft 3.

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The forums: http://z3.invisionfree.com/Fantasy_Bricks/index.

1.  Molds are made by creating a box out of lego, putting your original piece on the inside (I full the inside of the helmet with clay, and build a "body" of clay to stick to the base plate).  Then you fill the box with the silicone mixture.

2.  I make my original head/helmet out of a modeling compount, called Magic sculpt. 

3. As for the best resin to use.... depends what you want to do with it.  I use Alumilite white, which is the slowest setting they have; takes about 3 minutes to set up.

4.  The resin, silicone, mold release, metallic powder, everything is all from a company called alumilite.  www.alumilite.com

5. It is possible to cast some minifig parts.... if all you need is a head, you can probably do that.  But I'd say that most other parts probably aren't feasable.  But, lucky for you, most minifig parts are available in purple (except hands, curse you TLC!  My Magneto is incomplete!)

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

How could I do a LEGO Hood? Ayden if you ever make Night Elves from Warcraft 3 Please Pm me with the links. I love Warcraft!

 

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A lego hood can easily be molded with silicone and cast in resin.  Tothiro has done it already, and you can either ask him a specific question on the technique he used to produce it, or purchase one from him.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

Tothiro, what clay product do you use when creating custom accessories? What tools do you use to make them, and how big of clump of clay do you start off with?

 Also, how can I order your stuff.(Sorry if I got a little off-topic)

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Just one breath... incase that's all that is left...

BJ, since I haven't seen Tothiro in a while I'll try to answer your questions:

What clay product do you use when creating custom accessories: I use Magic Sculpt, and I think he uses milliput, both are about the same thing.  It's not a clay (which has to be heat hardened), but a chemical compound, which sets in about 2 hours, and cures in 24 hours.  Its what I'd suggest you use.

What tools do you use to make them: I use dental tools (most dentists have lots of worn ones they can't use anymore, just ask them), a leather awl (basically a sharp pointy piece of metal on a handle), an x-acto blade, and anything else I see around.  Just experiment. 

How big of clump of clay do you start off with:  Start small and mix more if needed, the stuff is only good for 2 hours.  I'd say the size of a pea is a good start.  Lego stuff is small, and if you're building on top of something (like a lego helmet) you won't need too much.

If you need to get in touch with Tothiro, best guess is to PM him.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

I didn't get part of the tutuarial on molding. Do you put the custom piece on a clump of clay then put it in the lego built thing or do you have to cut the helmet or something like that?

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Just one breath... incase that's all that is left...

No cutting of the helmet is required.  I'm doing some molds here soon, and I'm going to take pics for a tutorial.  So, just be patient and I'll post it soon.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

I have a twi'lek who desperately needs a new lekku (head tails) 'hair'piece. My question is if there is any way to make a flexible piece that will still fit on the head instead of making a solid piece from resin or sculpey.

I was thinking that it might be possible to cast a silicone piece inside the silicone mold. Have you tried anything like this, or read of anyone who has?

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So full of hate were our eyes that none of us could see

Our war would yeild countless dead, but never victory    ---   Covenant writ of union, canto I

I've not heard of anything like it... the problem with trying to cast silicone with silicone is that they stick together.  Permanently.  We use a mold release and paint it on parts we dont want to stick together when making a 2-part mold, but that's only on small areas.  Not sure the results would be good with a large area, and if it doesn't work, you've just ruined a good mold that probably cost a lot of time, effort, and money to create.

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Emily J. Brownlow

MCN Supervisor Moderator

Leader of the Sneaky Forum Ninja Assasination Squad

~Custom Cast Helmets and Hairpieces~

Okay hers an new question.

what brands of modling/asting products are the best?

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- Daredevil - Moderator of MCN

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