The first thing to remember is that Sintra is a brand name. The actual name of the product is
"Rigid PVC Foam board"
If you order "foam board" online or by phone, be absolutely certain that the dealer on the other end clearly knows, that you're talking about "Rigid PVC Foam Board" Not Foam Core Board! (There in a significant price difference!) Foam board is a generalized term for all types of foam core sheeting. If it is not clearly understood by both the suplier and the customer on the spesific item, you may be sent a shipment of paper backed styrofoam sheet.by mistake.
The PVC foam-like material is usualy used to create signage and displays. It comes in 4x8' sheets of various thickness and color. Sintra can be found at most plastics or sign supply shops (Check your area yellow pages under sign shops and plastic distributors for information on purchasing Sintra).It is recomended that you look for 1/8inch sheets of Sintra to make your costume, although you should decide what thickness is best for you.
The great thing about Sintra is you can make just about anything with it. It's durable, easy to mold (providing you buy the 1/8" thickness), and holds paint very well. It can be molded without expensive presses or vacuum tables. All you need it a big pot of boiling water and cold tap water nearby!
Tips on Working with Sintra.
First you should make cardboard test pieces of your armor to use as templates. These will allow you to "fit" your armor to your body shape first and not waste the Sintra. After you have the right size, trace your templates onto the Sintra sheet using a permanent marker.
Now it's time to cut out your pieces.
Use a Dremel or similar tool with cutoff sanding wheels for cutting through Sintra
Try to avoid using the cordless versions of the rotary tool, battery power will run out too fast. Possibly leaving you in the middle of a cut. The Dremel or similar rotary tool, with it's variety of tips available is one of the most essential tools for cutting and constructing your costume. This one tool will eliminate the need for jigsaws, grinders and beltsanders.
When cutting the pieces out, be sure and leave a 1/16" or more outside the line. The dremel will also leave some burs on the plastic, but don't worry about that at this point.
Now it's time to mold your armor.
Most suggest to boil the Sintra Pieces on an electric range or gas stove. To do this,you mus tfirst bring a BIG pot of water to a low boil. Try to use the largest pot possible for the larger pieces. (The bigger the pot the better.) If you're working with small pieces, a smaller pot will be fine.
Turn the faucet on cold water and have it running and ready. When the water starts to boil place your pieces One At A Time in the pot for 10-15 sec. The longer it stays in, the softer the piece will become. Use tongs to remove the piece and bend/mold it to the desired shape with your hands. The Sintra will be hot, but it's usually not so hot you can't touch it. If it is too hot, wear some gloves.
MOST IMPORTANT- while you're holding the armor to the shape you want, run COLD tap water over the piece. This freezes the molecules in the plastic and the Sintra will hold it's shape. One of the best aspects of Sintra is, that if the shape you just formed is not exatly the way you want it, just repeat the process until you get it right. Once the pieces are formed correctly, you're ready to proceed.
Next step is to remove any burs and smoothen the pieces.
Use a flexible sanding block with heavy (40) grit finish to remove the burs and straighten the edges. This will sand the shape quickly, Then, once it's close to the desired shape, move down to a 100-300 grit paper to bevel the edges to a smooth finish. Continue to lightly sand the entire surface area, creating a very slightly rough surface for the paint to stick to. Aditionaly if you choose to, the prep work can be finished by using the dremel with a grinding tip to "dent" your armor pieces. Be careful not to do too much or sand through the pieces.
Here are some more techniques for use with Sintra:
For most joining of multiple pieces, you can use a clear two part epoxy glue. It is in a plunger type dispenser, where pushing on the plunger squirts out equal parts of resin and activator, which you then mix together. It dries harder and
thicker then super glues, and is not as brittle.
If you want to secure two pieces of pvc foam (Sintra) together or a piece of styrene to Sintra, One recomendation is, a product called "PVC to ABS transition cement" by Oatey. It is found in the plumbing section of hardware stores. The great thing about this is that it's white, so there's no color problems of any kind.
One important note is: It melts the plastic (be it PVC [like Sintra] or styrene) so when you secure two
pieces together, you end up with one.
If this cement drops where you don't want it, DON'T scoop it now, or you'll end up digging a hole in your plastic. Take a
piece of cloth to absorb the excess, then wait for a day or two for the plastic to harden back. You'll now be able to sand it to the perfect surface it was before.
When in doubt, make a small test.
To build up the surface, or fill in seems, Use 20-30 minute variety, two part expoxy putty. This putty is a mix of two different colored putties together until it's one uniform color, after you mix the two parts. Take the clay-like substance and fill in the seams, or sculpt the raised area you are trying to achieve. Epoxy putty also can be used as a
"glue" but it's usually a little too thick for that purpose, unless you put it BEHIND the area you need joined. It provides a strong bond and helps reinforce the joint.
A great technique for a acheving a smooth surface with epoxy putty ( especially the edges for better blending) is, instead of just wetting your fingers with water to smooth the stuff down, take VICKS VAPO-RUB and use it to smooth it out. It really helps lessen sanding later. There are solvents (mineral oil and turpentine) in Vapo-rub (or a cheaper generic
equivalent) that are believed to be the factors that allow this to work so well.
This same technique can be used with "squadron" type model putties or red
auto putties, by replacing the "Vapo-Rub" with fingernail polish remover.