Trooper Cooper
Well-Known Member
My main armour and prop maker/finisher, Ed Woodward, made a post in the Operation Chastity thread about how he made the original casting of our Marine helmet. Following comments in the thread, I'm posting this on his behalf here. If and when he gets Veteran/Elite status he'll be able to post stuff here, but in the mean time, I will be posting his updates. Enjoy!
Master Cheeze said:Hi guys
This is an update of my tutorial from the original post on the Operation Chastity thread containing new images and info on how to sculpt, mould and cast our marine helmets in fibreglass. To fill in the gaps I have used other images from other jobs to complete the process in this tutorial. I hope this all starts to make some sense...
Thank you for reading.
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Sculpting.
To begin with I scanned the images from the source book that I am working from; in this case it is helmet profile concepts in The Art of Halo 3 book. Once I have the profiles scanned I then scale them up in Photoshop to a relevant size that would roughly fit a head, knowing that the final size and look will probably differ to my starting point. My experience in working with different clients is that people like to change things here or there to make it suit their needs and also when working from 2D references you find that some of the angles don’t add up and you have to translate from one image to the next to create the desired aesthetic. This is just a starting point.
When I am happy with a size, I then print the profile out. To get the right size the image needed two sheets of paper as the image was too wide for one. I then stick the image onto a piece of card, foam board or whatever I have handy at the time and cut it out. I now have a solid profile to work from.
The clay that I am using is a wet pottery clay available from any pottery craft suppliers and from most supplies of your chemicals. I use this because it is very quick to map out a job and get a general idea of the shape. Now there are generally many types of wet clays available some more gritty and others softer - ask for a modelling clay when calling to make an order. The clay I used is actually called Buff Stoneware 1117 -. Check out PotClays LTD or Alec Tiranti's if you are in the UK. If not in the UK then you can get some idea of what to ask for by clicking the links anyway.
With the card profile I then go to a head cast I have handy of a friend and start sculpting, holding the profile up over the centre of the head, adding clay to fill in the gap between the head cast and the card profile. (Here is an example from another job, but instead of a poly core, imagine a fibre glass head.) With the profile in place I then very quickly map out a very very rough shape.
From here there is a lot of sculpting bits, taking pictures and sending them to the client, making changes, taking pictures of the profile of the sculpt and comparing them in Photoshop with the concept art profiles scanned.
In doing this I noticed that the initial profile that I made earlier was too big, so I matched up the chin and nose of the head cast with the chin and nose of the scanned concept art to work out what needed removing and changing. Also putting your work into Photoshop and comparing it with the source material regularly is a very good method of seeing how far out you are from the source. To do this, load your image into Photoshop and layer the concept art over the top of your image and change the opacity of the concept art to see your image underneath. You may need to adjust the size of the concept art to fit over your image. You also can take a picture of the profile from the other side of your sculpt, flip the concept art horizontally and compare the other side.
To check the balance of your sculpt you can do a similar thing. Take an image of the sculpt from the front, load into Photoshop, copy the layer or image, flip one horizontally and place that one over the other in a similar way to the profiles, changing the opacity of the top layer to see the other. Then you can decide which bits you like and change the rest accordingly. (...I hope you all got that.)
I also did the same with the other concept art, as we wanted to move more into that direction.
We had already decided that we wanted the helmet to resemble the in-game helmet but keeping in the style of the concept art in the book.
With the balance and the shapes right I could get on with detailing. We deliberately wanted the strike plate off at this stage, to be sculpted later, so that the helmet could be customised to bring character to our armour.
To finished the sculpt I smooth the clay with a selection of metal scrapers and Kidney's, rubber Kidney's and scraps of upholstery foam used as a sponge
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Moulding: First stage - Silicone.
This method that I am demonstrating is a variation of many methods and is best when working with wet clay. Wet clay shrinks over time as it dries out which can be a big problem for moulders. This method seals the clay from the beginning with the first layer of silicone. Sculptor Philippe Faraut uses a similar method using paper in his first book Portrait Sculpting: Anatomy & Expression in Clay.
Firstly before I do anything I need to prepare the sculpt for moulding. I built up a wall around the nose with clay and connect it to the neck. The design of this wall has a dual role, firstly it cuts out the face from the mould so I am not wasting materials and secondly this enables me to have easy access to inside the mould for casting in fibreglass later.
With the clay wall in place I then mix up enough silicone to cover the sculpt with a thin layer. Try and poor from the top letting the silicone do all the work. You can help it with a brush, but be careful as the brush can create air pockets and dragging it across the clay can leave marks. Blow the silicone into any details to make sure you don’t get any air pockets in them. Then leave to cure. Don’t worry about overflow as you can clean that up later.
I had decided early on in the process that I wanted the mould to separate along the line of the profile. This makes it easier to cast in fibreglass, as I can laminate in the two sides, then close the mould and laminate the join. To make that separation I am going to use 1mm plastic shim which comes vac formed with keys and is clear. It is available from W. P. Notcutts.
The shim is stuck to the first layer of silicone with a small amount of silicone mixed with a Thixotropic additive (used to thicken silicone). Scoop your mix into a small bag and cut a hole in one corner. Squeeze out the silicone along the line where you want your seam to be. Later when you come to de-mould you will cut down this line to separate the silicone making the two halves.
I cut the shim into pieces and push them into the silicone line, placing them one after the other, offering them up and trimming them here and there, overlapping the edges as I make it round the mould. I use Sellotape to stick the pieces to themselves and thus they hold their own shape and stand perpendicular to the sculpt.
Once all the shim is on I then smooth out the silicone so that when I apply the next layer I am not caught with air bubbles between them. I use brush with Isopropanol Alcohol (IPA) which is a cleaning alcohol that evaporates and does not affect the silicone. It does not leave any residue on the surface that you would normally get if you used washing up liquid or starch from a chopped potato.
With the shim secured, ceramic keys are glued onto both sides of the shim at regular interval with silicone. You can make your own out of balls of clay, moulding and casting them in a hard material. However, these are also available from W. P. Notcutts as they are part of the same system as the plastic shim.
As I build up the layers, the keys are buried in more silicone mixed with the Thixotropic additive over the mould and then smoothed.
When I am happy with the thickness of the silicone I then trim the edges back to reveal some of the shim. This is where the two sides of the fibreglass jacket meet each other and later can be drilled and bolted together without anything in the way. The ceramic keys are then revealed and removed from the silicone leaving a hole where they used to be. These holes are filled with resin when making the outer jacket creating a key for the silicone to lock back into the jacket stopping it from coming away at the edges after demoulding.
I now prepare for the fibreglass.
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Moulding: Second stage - Fibreglass*.
The outer jacket of my mould will be made using polyester resin that has been reinforced with chopped strand matting (glass fibres woven together - fibreglass). You can use the glass fibres in many other materials like polyurethane resins and even cements. It is not limited to just polyester resins. The glass strands in a roll of fibreglass are held together by glue which makes a sheet rigid, the glue is broken down by liquid, softening the glass strands to be moulded around shapes. Glass fibres come in many forms of mats and weaves but generally moulds are made with the chopped strand matting as it is cheaper than the rest.
Polyester resin comes in two forms; a Gelcoat and a general purpose/laminating resin of which you will need both to complete the GRP system. The Gelcoat is applied first as it is a thicker material (higher viscosity than the laminating resin) used to pick up detail and fill in the around the silicone jacket in order to give the matting an easier surface to be laminated on. The laminating resin is used to wet the matting so that is can be applied over the Gelcoat.
In this Image I have a pre-pigmented grey Gelcoat (left) and a clear/opaque laminating resin (right).
The catalyst/hardener for Polyester resin is an organic peroxide** - methyl ethyl ketone peroxide, generally sold with polyester resin. Your supplier will sell you the correct hardener for their resin.
The mix ratio for polyester resin to catalyst is usually 100:2 percent, either by weight or by volume, in a normal working environment. However, depending on your working environment at the time you might want to add more or less catalyst. A colder environment will slow the chemical reaction between resin and catalyst, so one might add more catalyst, up to 3 or 4 %. If in a warmer environment you may put as little as 1 or 1/2 % catalyst as the warmth will accelerate the chemical reaction. The chemical reaction is exothermic meaning that is gives off heat as it cures. Any leftover resin mixes poor away into a bucket of water. Not down a drain.
When working with resins you must prepare any surfaces on the job that they will be in contact with, whether it is part of an armature, base board or more importantly: other fibreglass - like the shoulders of a head cast for instance. A wax or a suitable release agent is used to prevent the resin from adhering to your surface. I use a liquid wax that can I apply three layers evenly over the surface with a brush, letting each layer dry before applying the next.
- The next load of pictures are from another job that I had moulded in exactly the same way. The Gelcoat on this job was pre-pigmented to white ivory. Don’t ask me why. The boss bought it in.
The base board was waxed and a generous layer of Gelcoat, mixed slightly more than 2%, was applied over both sides of the mould. I have to then leave the Gelcoat to cure for a while until the surface gets tacky before I can start laminating.
Keep an eye on it, the Gelcoat will go from workable to rubbery to cured. I want to catch it before it between rubbery and cured to reinforce with the fibreglass. If I start laminating too early I will disrupt the Gelcoat and it can peel away from the surface.
Make a cup of tea, play some Halo or cut out the fibreglass matting into pieces.
When the Gelcoat is ready, I mix my Laminating resin with slightly less than 2% catalyst. Mix up enough to cover the whole job with 2 to 3 layers of fibreglass and brush a layer of Laminating resin over the Gelcoat. If I don’t have enough resin to complete the fibreglass I just mix up another batch with slightly less catalyst again and continue.
Some moulders may sprinkle chopped strands (loose glass fibres) over the Gelcoat first and then brush on a layer of laminating resin. Sometimes I use chopped strands but I did not on this job.
Then soak your matting pieces and lay them onto your mould. With a loaded brush, pat the matting down, working out all the air bubbles
Lay another piece next to the first, overlapping the edges, working them together. Do this over the whole mould.
When I have gone round the mould 2-3 times, I then put a finishing tissue over the top. The tissue is very fine and will be used to soak up any excess resin and make the surface of the fibreglass nicer to handle later. Tear the tissue into workable pieces and place them all over the fibreglass.
With a brush dab the tissue and let it soak up the resin. Work from the centre and chase the air bubbles out to the edge.
Using tissue, the surface of the fibreglass will go clear and you will be able to see right down through the layers to the Gelcoat. When I cannot see any more air bubbles I know that I have done a good job.
Leave to cure. Overnight is best, come back to the job in the morning.
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Moulding: Third stage - Demould.
With the resin cured it is time to demould. Firstly drill bolt holes evenly around the edge of the mould with a 6mm drill bit to fit M6 bolts (these are in metric). As long as your bolt fits the your drill hole, you will be fine. Then cut away any excess fibreglass with a vibrasaw, reciprocating saw or a hack saw. Wear a mask to not breathe in any of the dust.
With a power file or sandpaper, clean up the edges.
Pry away the fibreglass jacket from the silicone and pull out the shim. Then with a new sharp blade separate the silicone and cut along the seam line.
Clean up the clay out of the silicone and then lock the silicone back into the fibreglass jacket.
Put the mould back together to inspect the seam line.
That line will disappear when the jacket is bolted together.
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Casting: Fibreglass.
For this section I recast the helmet and took pictures of the relevant steps. The Gelcoat used is the grey Gelcoat from the image I used to introduce the polyester resins a couple of sections above. It was new stock as I had run out of the previous stock I used for this demo initially.
I mixed up a small amount to cover the two halves evenly making sure not to go over the seam edge. If I do, I carefully wipe away the excess before it cures. I don’t want anything to get in the way of my seam.
Again I waited until the Gelcoat went tacky.
And then sprinkled some chopped strands. I used them this time to show you how to. It is just an extra step the some moulders do to help the fibreglass layers bond to the Gelcoat. Some moulders prefer not to use or dislike using chopped strands.
Mix up the laminating resin and paint it into the mould with the chopped strands. Then wet the fibreglass pieces and laminate up to the seamline taking care not to go over it.
When I have laminated both sides I wipe away any splashes and bolt them together.
Paint some resin onto the seam line (you can rum some Gelcoat along the seam instead if you like), wet some strips of Fibreglass that I had prepared earlier and laminate them into the seam.
Leave to cure.
When cured I can then demould and hope that all went well.
Trim the fibreglass with a vibrasaw or reciprocating saw and the finish the trimming of with a power file or sand paper. Then find a test subject to see if it fits.
- If I had not made the clay wall around the nose before I started moulding I would not have been able to get inside the mould easily with my materials or brush. However, when working on a closed mould, I would have made the join differently - but that is for another topic.
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*Please, when using Polyester resins/plastics or Polyurethane fast set resins/plastics of any type, wear disposable paper overalls, a respirator, gloves and even goggles to avoid contact with eyes. Use the chemicals outside or in a well ventilated area. Not a bedroom or a kitchen! Even more so with Polyurethanes (as they seem to be the preferred casting choice on this forum) as a lot of them are odourless and can seriously damage health.
**Avoid contact with skin and eyes.
If you want to live till they start colonising Reach? Get protected!
Happy making. *thumbs up*
Master Cheese.
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