Wednesday, October 06, 2010

Hobby Tips - Green Stuff Moulding and Casting Tutorial

Hi Folks,
Today is the first in an infrequent series on the various hobby tips I've picked up or developed over my time playing and modelling. Hopefully for some people this might be useful but for those of you that are old hats at this modelling malarkey please feel free to offer tips and suggestions as to how to improve my tutorials and the techniques I use. Also as a heads up as I'm still only at the modelling stage of my current project most of my first tutorials will deal with this, painting will come later.

I've been asked a few times in the past how I recreate some of the icons I've used, how to replicate an icon from a shoulder pad or even how to cast an item off a flat piece for use else where. So I decided to make my first tutorial a quick guide on Moulding and Casting with Green Stuff.

To begin moulding and moving on to casting you will need a few items and I have cut my list down to the bear minimum for speed and cost. To make a successful mould you will need:
  • The Item you wish to mould
  • Blank Shoulder pads or items you wish to cast on to
  • Green Stuff
  • Cutters
  • Hobby Knife
  • Kitchen roll/towel
  • An old paint brush
  • Tweezers
  • Some kind of lubricant

As you can see from the list and the picture this is not a huge list and certainly only covers basic simple push moulds rather than two part moulds. Once you have all these bits assembled you can then start on the following step by step guide on how to create a mould and then cast the icons in question:
  • First job is really simple, all you need to do is decide on the the items you wish to cast, in this case I will be using the two shoulder pads that Ron over at ++From The Warp++ sculpted for me for the Red Hunters and the Mentor legion. Using these is twofold, 1- they aren't produced by GW so don't break any copyright and 2- I need them for my upcoming marine forces. Once you have the items its prudent to check them over and remove any flash on the pad and tidy up any rough areas on them to help produce a smooth lift from the mould, this is illustrated below:
  • Next step is to measure out the green stuff you require to cover the whole front of the pad to a depth of around 3mm and to give an excess all the way around the rim of the pad to roughly 3-4mm, this is a ball of roughly 1-1.5cm in diameter. Leaving an excess round the edge gives you something to hold on to when removing the pads and the depth assists when you start casting later and means you don't end up pushing the green stuff through the front of the mould. As you can see from the picture below I do a little extra prep on my green stuff:
    As you can see from the picture I have cut the amount required, I have then cut the thin strip out where the two separate parts of the GS meet. This is something I recommend doing to help give a smoother putty to work with. I have found that sometimes if you have an older batch of GS the section where the two colours joins has often started to cure, by removing this it makes it easier to kneed the GS and gives a smoother finish, slightly wasteful I know but we're going for results here!

  • Once you have mixed your GS the next step is to take your Old Paintbrush and use it to apply a liberal coat of lubricant to the front of the item you wish to cast. There are various types of lubrication you can use but I personally recommend anything water based, this makes it easier for washing off later and means you can make other moulds or even paint on to the item easier.

  • Once liberally coated the next step is to push your pad in to the freshly mixed GS, I start by making a rough ball of GS and slowly pushing the pad face down in to the top of the ball. I make my best effort to get the centre of the icon in to the very top of the ball, this just makes sure the GS covers and fills the detail of the icon and helps locate the pad in the center of the GS, once completed the pushing the mould should look like this:
    As you can see at the top and sides I have left a 3-4mm overlap with the GS coming well clear of the edge of the pads, this gives me something to grip for removal and something to push against later for casting.

  • Once you have finished the pads you should leave the moulds in a warmish place for 36+ hours, as I knew these would be getting some punishment I left them for just over 48 hours just to ensure they were fully set and rock hard, do not remove the pads from the moulds before this time as it means they do not support themselves properly and are likely to deform.

  • Once this period for setting has elapsed you can then remove the pads from the moulds, to do this you can use your cutters, tweezers or fingers to grip the pads and pull, there is also still some give in the GS so you can at least try to tease it from the edges of the pads. Once done you should be left with something like this:

    I would then recommend leaving the moulds for a further 12-24hours to make sure the inside of the mould which was protected from the air by the pad and lube has fully cured. This isn't necessary but its a useful suggestion to prolong the life of the moulds

  • Now the mould making process is complete you can begin on the casting. This is where you will need you blank shoulder pad. The first step is to mix up a small amount of GS as shown here:

    As you can see from the 6mm airsoft BB in the picture the ball of GS required is somewhere between the size of a Space Marine Shoulder pad and a 6mm BB.

  • Step one of the actual moulding process is to take the mould you wish to use and cover the relief image of the icon and all of the internal part of the mould with lubrication:

    Feel free to be fairly liberal with the amount you use as any excess lubrication should squeeze out when you start the push casting.

  • Next take your ball of GS and push it in to the mould gently, to ensure I roughly cover the whole of the icon before I start on the pushing I put a small amount of lube on the round end of the paint brush and push the GS gently until I end up with this:
    as you can see this doesn't quite cover the whole of the inside of the mould and is still pretty uneven but this will be rectified soon.

  • THIS STEP IS PURELY OTIONAL - this step can be used if you want to make sure you are covering the icon but is not required. If you would like to make sure it is covered then take your old brush and with the round end use it to gently push the GS to cover the icon impression. If you have found you havent put enough GS in you can add more at this point to cover the icon and repeat the brush push stage. one thing to note is that this step can occasionally cause slippage so personally i wouldnt recommend it be some people find it useful.
  • Once you have done this place the shoulder pad in to the GS and gently push, you should then end up with this:
    As you can see the excess GS and lubrication has started to be pushed out from around the mould and the pad.

  • Next take the mould and the kitchen roll/towel, place the mould on the roll/towel with the pad facing down (if the pad was uncovered you would expect to see the icon facing up towards you. Then gently apply pressure to the mould and push down as hard as possible but slowly and gently. keep this up for 30 seconds to 1 minute and you should have like below:

    here you can see the excess lubrication and GS has being fully squeezed to the side of the pad and should be completely pushed in to the icon.

  • Once this is completed you should now have a small amount of GS left over from what you moulded up, I personally use this to make rudimentary sandbag shapes for future terrain, you should therefore be left with this:
    there seems to be a lot of excess GS sticking out from the mould but this is actually more of a bonus than it seems as it means you now have something to grip to help remove the cast from the mould.

  • This step is nice and simple, leave the pads in the moulds for 24-48 hours to allow the GS to set and to make sure the icon stays crisp.

  • After letting the GS set you can then use your cutters, tweezers or fingers to grip the pads and pull, this sometimes removes the pad and the GS cast, often though it will just remove the pad and leave the icon in the mould. If the pad takes the icon with it I then use my tweezers to grip the excess GS and remove the icon from the pad, if it doesn't take the icon with it I use the tweezers to remove the icon from the pad by the excess. Once removed from the mould or pad you should have this:
    As you can see there is an awful lot of overflow but its very thin and easily removable with either cutters or a hobby knife.
  • The next step is to clean up the icons and if needed remove a small amount of GS from the rear of them, rinse them to remove any lube and then stick them on appropriate shoulder pads. Personally I wait until I have cast all the pads I need of a type before I tidy them up and mount them on pads.
Well folks there we have it the step by step guide on making icons for short runs of pads or the odd character. I hope this is of use to someone and gives you a good basis for future modelling projects!

As I need lots of both icons and pads my next tutorial will deal with making a silicon mould for casting larger numbers of self sculpted or custom sculpted pads, this is why there are no finished pads above but tune in again soon when once I have completed an additional 5 Red Hunters pads I will then show you how to make moulds of them for a more production line casting process.

Any questions, tips or requests feel free to drop me a line.

**Please Note to comply with the GW copyright rules (and to cover my arse!) this is only to be used for casting either self sculpted or commissioned icons or casting icon that are part of a larger item - please do not use this to cast and replicate parts or icons that are readily available from Games Workshop**

1 comment:

Da_Sub said...

Indeed this is a very neat technique, I used it to make ten copies of the 13th Company Shoulder marking I sculpted up to make ten shoulder pads that could then be cast out of resin to do my whole army (40 marines).

Nice walk-through!

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