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The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It is used in a variety of materials from floatation devices to insulation to packing material, and as such is often readily available. Certain kinds of foam are also useful for doing any kind of modeling, and that extends to the creation of props and costume armor.
There are several advantages to working with foam:
- Foam is lightweight
- Foam is easy to work with
- Foam is relatively inexpensive
- Foam is ideal for building up intentionally bulky pieces
- Foam is safe because it uses no caustic chemicals and produces no toxic vapors
That said, there are a few disadvantages to foam as well:
- Foam is delicate
- Foam is poorly suited to making thin pieces
- Foam can require a lot of time and labor to be invested
- Foam does not leave a lot of "hollow space" in which to put other things
The two kinds of foam that should be commonly used in armor making, insulation foam and spray foam.
Insulation foam is fairly generic and tends to come in either pink or blue colors, neither of which is signifigantly different from the other. It can often be bought in tile-like sheets and can be found at home improvement stores. This will comprise the bulk of what is worked with.
Spray foam comes in a can and can be used like caulk, ostensibly intended to fill in cracks. That will be one part of its use in forming armor or props, filling in gaps between the larger pieces of insulation foam. However, its full usefullness can extend well beyond that. It will adhere to most surfaces and can thus be used like a form of "foam glue", causing objects it is sprayed between to stick together. This can be used to glue larger pieces of insulation foam together to allow creations that are deliberately bulkier in places. It can also prove useful in fixing mistakes made during carving. If a crafter carves too deeply and removes portions that were intended to be there, the spray foam can be used to build it back up so it can be carved down again correctly. However, it is advisable to use this last method somewhat sparingly, since the spray foam tends to be more expensive per unit of volume than insulation foam and it would be undesirable to waste it. Great Stuff Gaps & Cracks is one recommended spray foam brand.
Filler is a generic term for most kinds of epoxy-based products designed to be poured or smeared into gaps and harden there, Bondo being the best known example of it and an entire range of similar filler products are casually refered to as "Bondo" for the sake of simplicity. This will be essential for surface strengthening and creating smooth textures. There are newer kinds of filler which contain "micro-balloons" (essentially making the filler itself technically a kind of foam) which is advertised as being lighter than traditional foam, and a crafter may want to consider it for their projects for the sake of that lightness as filler adds perportionally a lot of weight to any finished product.
Cheesecloth is also recommended. It can be purchased from culinary supply stores and some fabric stores. While cheesecloth is ostensibly used in cooking as a material for straining liquid from solids (primarily letting milk curdle into cheese and thus the name,) it can also be used to great effect in strengthening the surface of foam crafted items. In this regard, it functions something like a "poor man's fiberglass."
Thin kinds of hard plastic should also be near-essential to form armor for strengthening purposes, and PVC piping can be used to the same effect when crafting foam weaponry. It is recommended that a crafter use these things when making foam items, and they should be added very early into the crafting, possibly forming a core component of the finished product. It is very difficult to add them after a product has already been made, so good planning is essential to their integration. It also makes an ideal place to attach straps and other load-bearing items since it will not tear appart under weight like foam. The plastic can be purchased in large rolls, and the PVC can be bought as pipes from a variety of home improvement stores.
In the case of armor components, a few small pop rivets will probably be necessary both for shaping things like plastic backing and affixing hardpoints to latch straps to. Flush-headed hollow rivets are recommended for use when crafting foam armor. Be sure to get some rivet washers to help keep the rivets in place.
The essential tools for working with foam will be a sturdy craft knife, sandpaper, a bucket of primer paint with a good brush, and for some armor a drill with a bit fitted for the size of rivets used.
Unlike some materials, creating foam props and armor does not require a large, well ventilated area, nor does it require any wearable protection such as gloves or fume masks and is completely safe. However, it can produce lots of debris, so it is recommended that it be crafted over a removable and disposal surface such as old newspaper for the sake of cleaning it up afterward, and one should have a vaccum on hand to get rid of any tiny pieces or dust. Knowing some basic knife safety such as "always leave the blade retracted in when not in use", "do not run while holding a knife", and "while cutting only apply force in a direction away from your body and fingers" should go without saying. A dust mask may come in handy for preventing irratation caused by dust from sanding, but is no more so than any other kind of dust. Also, some people report having headaches around drying spray foam, so it is recommended that one wear a mask when spraying it and leave it alone to dry.
The first thing to do when crafting with foam is to figure out how to "base" the object being crafted. This is where things like plastic and PVC pipes come into play. Foam can be delicate, and while the surface can be strengthened against damage as described later, even with that a small amount of force leveraged in the wrong place can snap a foam component in half. Good basing will prevent this unfortunate happening.
In the case of armor, a plastic base can be used as the underside to foam plates. Shaping it to fit the body can take a little work though. Often, narrow triangular cuts known as "darts" can be placed from edges of plastic pieces, allowing it to be bent around in a semi-curved manner and thus fitted to the approximate shape of a body part that the armor is designed to cover. The plastic will want to spring back into shape, so it is best to temporarily seal the edges of a dart together with tape, then use something like a rivet to affix the sides of a dart together along with some bonding agent like glue. If there are some hardpoints where straps are to be connected, then these should be rivetted to the plastic at this stage as well, preferably with three to five rivets each for load-bearing reasons. The rivets should be placed so their heads are facing "inward" on the side of the plastic facing the wearer's body, and their tails facing "outward" away from the wearer's body.
Once the plastic has been formed to satisfaction, a crafter can then begin placing down foam. Pieces of insulation foam should be put down and stuck in place by spraying the area underneath them with some spray foam. If there are any rivet tails sticking outward, the foam can be pressed onto them which both covers the rivet and helps keep the foam in place. If the plastic is curved then one should not expect the insulation foam to be flush with the plastic, but that is okay since the spray foam is intended to fill in those gaps. The insulation foam can approximate a crude "curve" by cutting the edge of it so that its narrow side is diagonal relative to its wide side and pressing that up to other sheets of insulation foam already stuck to the plastic. Do not be afraid to build the foam up higher than one would expect the surface of the armor to be at any given point, and it might be wise to build up the foam higher than one thinks it actually should be. This will be carved down into shape, and it is always easier to have too much and whittle it down than it is to have to little and have to build it back up. When placing multiple layers of insulation foam, use spray foam to "glue" each one down to the one below it. Feel free to cut up different shapes of the insulation foam to fit into different places. Many pieces of "cast off" insulation foam from a piece placed in one area can actually be used to build up another area, so try to keep large cut off pieces of it on hand until you are sure you will not find use for them.
Once the foam has been built up, leave the spray foam to dry for several hours and then return for the "meat" of the project, carving. Whittle away at the foam with a craft knife like one would if one was carving a foam statue of the component in question. Go slow and do not cut too deeply too quickly or one risks making mistakes. It is easiest to concentrate on one area of the component for a time, then move to the next area, then then next, then back to the first, getting closer to the intended shape with each "pass". This helps keep different sides of the component even with regards to each other and will assist in keeping the component to a uniform standard of quality. Once it is sufficiently carved, use sandpaper to rub out the rough spots in the foam and get it to its near final shape.
The same proceedure outlined above for armor also works for weapons, but the basing is different. For most conventional weapons, a core of PVP pipe is sufficient to build the rest of the foam weapon around. There may be some initial carving done in the insulation foam at first to allow the pipe to fit between two or four pieces of insulation foam "sandwiched" together and stuck with spray foam. Whittle it down from there as above. For more exotic weapons, a single piece of PVC pipe may not be enough, and several narrower PVC pipe pieces may be required or combined with other materials. This is a greater engineering challenge and should only be attemped by those with some prior experience. An inexperienced crafter can still try, but should expect frustration along the way.
The suface of foam leaves an obvious foam texture which will probably need to be covered up, but is also delicate and prone to damage unless reinforced. This is where items like cheesecloth and filler come into play.
Cheesecloth can be applied like fiberglass, but is a lot safer and easier to work with. Simply place cut sections of cheesecloth over the component and press it down so it is flush with the surface, then paint over it with primer. You may want to put a layer of paint on the surface of the foam and then press the cheesecloth down into the wet paint before painting another layer of primer over it as an additional measure. The paint will cause the cheesecloth to stick down to the surface of the foam, and will stay there of its own accord after that. The paint will also cause the cheesecloth to harden somewhat, leaving a slightly tougher surface, and will also keep the foam pieces together in the unfortunate even that it does break, concealing the break and making repairs somewhat simplier. Cheesecloth works best when drawn in large pieces over relatively flat areas. If used on a more complex surface, some pieces of the cheesecloth might need to be cut in a few places to get it to lie flush with the surface. By pulling on the diagonals of cheesecloth, one can get it to be taunt in the middle and slack in other places. This is useful when trying to get it flush over a "bump" in an otherwise regular surface. Try to cut larger sections of cheesecloth than are absolutely necessary for the size of the surface, the sides of it can be trimmed off once the paint dries.
Depending on the look of the component being built, it is possible to stop at this point and move onto the painting and detailing stages. The presence of the cheesecloth will leave an obvious cloth texture to the surface, but that can also be used to give a kevlar-like effect that might be appropriate for certain costumes. However, if a smoother texture is needed, a final step is required, and this is where the filler comes in.
Filler generally takes several hours to harden once it is mixed as epoxy, and very little of the catalyst is necessary, so there is a lot of time available to put it on the component. That said, it is still preferably not to mix too much filler at once. The filler can be applied to the surface of the cheesecloth or even the raw foam if cheesecloth was not used. Try not to use too much, as filler can get very heavy and not a lot is actually needed, just enough to cover up the surface. Once the filler has dried and hardened, sandpaper can be used to smooth the texture of it and leave something worthly of project Mjolnir.
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