Before you start anything, make sure that newspaper is laid down where you are working, that you are wearing gloves, protective mask, goggles and that hair is tied up. The extraction should be on as well.
Once you have a mold to make the helmet from, you need to prepare the mold ready for fiber-glassing. This is so that the resin does not stick to the mold and you are able to separate the two when you are finished.
For this you need either a Universal Mold Release Wax or a Wax Parting Agent. Both is not necessary. Apply this to the inner surface of your vacuum formed plastic helmet, give it a few good coats and buff well in-between coats and allow a good 10 minutes to dry.
Once dry you need to apply a coat of blue gloss and allow this time to dry. Once this is completely dry you need to spray on a coat of mold wax spray.
To make the resin you will need a gel coat and a catalyst to speed up the reaction. These are mixed in a ratio of 100:1. Therefore for every 100grams of gel coat used, 1gram of the catalyst is used. For this helmet, we are using exactly these amounts. Use the scales to measure this accurately. Remember to always zero the scales when you put the pot onto them, otherwise it will calculate the weight of the pot as well as the resin.
Mix these both together very well, and add in any metal powder if you wish to use any.
Paint a very thick coat onto the inside of the helmet mold. This should be around 2-3mm thick. You will need to leave this to dry now, which should take roughly half an hour. Once it is slightly tacky you need to start tearing up pieces of
Fiberglass matting and tissue into small squares.
Next you will need to mix your lay-up resin. This is in the same way as you mixed the resin earlier, as you will use the same catalyst and at the same ratio.
Add in some pigment into the mixture (no more than 5%) and mix this well. Paint a layer of this resin onto the helmet. Place some squares of the matted fiberglass on top of this making sure that they overlap. Press these into the resin so that it soaks through but make sure you do not brush it around as this will make the fibers spread around and leave gaps. Do a few coats of this matted fiberglass.
Make sure that there are no strands that are standing out and then you can move onto applying the tissue in the exact same way. You may need to mix up some more resin. Do this with the same ratios in the same way. Once you are happy with the layers leave it to dry and then cut around the rim of the helmet (not through the plastic) but so that there is no fibers protruding over the edge. This will make it easy to get a good grip on the edge of the helmet to pull it apart from the plastic mold. You need to do this when the resin has set thoroughly. I would recommend leaving it overnight.
Once you have separated the 2 the next part is to cut and sand away the bottom inch of the helmet so that it is smooth and has a flat edge. Using a hack-saw is the best way to get through the resin. Next, use sandpaper until you are happy with the smoothness of the edge.
To smoothe off the surface of the helmet, use a sheet of wet and dry 212 sandpaper with water and buff it until you are happy with the outcome. It is important to note that when you use this sandpaper without water you will need to wear a ventilaton mask as the dust is harmful.
After this, get a small pot and fill it with a solution of T-cut. With a small piece of cloth apply in small circles to the surface and buff off after rubbing it in. do this to the whole layer. This will help to remove small scratches and to bring out the metallic colour from the pigment added to the resin earlier. Buff it with a piece of wire wool inbetween coats of the T-cut. It should only need a few coats of T-cut but it is down to preference. If you are happy with the outcome then stop.
You now need to prep the helmet for painting. Apply a layer of primer onto the helmet and allow this time to dry. This will allow the paint to bind to the helmet and avoid it from flaking off. The next step is easy. Mix the colour you want for your helmet and apply.
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