Could you do us a favour and make a few pictures of that process and which materials you use?! As a non-passfire member its sometimes hard to get such pieces of information
Here are some photos of my setup: -
This pic shows the mold adapter for connecting the mold to a wet and dry shop vac, 1.75" and 2.25" fiberglass moulds, a batch each of the two size hemis and a piece of lycra swimsuit material as a mould filter. This material is much better than cotton for this purpose because it stretches under vacuum, perfectly conforming to the hemispherical shape of the mould. Because it stretches in use, it relaxes once the vacuum is switched off and helps eject the finished hemi.
This shows the huge amount of 1.5mm holes drilled through a 2.25" mould. A tedious job, but it only has to be done once!
A batch of 2.25" hemis. The only thing left to do is soak them in wood hardener to waterproof them. If this step is ommited the shell will turn to mush during the pasting process and all your hard work will have been a waste of time! Alternatively you could use a layer of masking tape or use any non water-based paint to coat the shell prior to pasting. However, it is less work to use wood hardener. Simply dip the hemi in a bath of the hardener and it will absorb all the way through the hemi with no need to go painting with a brush. Also the wood hardener is acetone based so it will dry very quickly. Remember to dry them away from sources of ignition!
The basics of the process: -
The mould is put on to the wide end of the adaptor, held on by the filter secured by an elastic band. This is then connected to the shop vac and switched on. The mould is then diped into a tank of mulch for a few seconds then removed. The time spent in the tank governs the thickness of the finished mould, so you'll need to try a few times to get it right! To eject the hemi, remove the mould adapter from the vac tube and blow down the adapter, the hemi will pop out without too much trouble.
I use cellulose insulation to make the mulch. This is a fluffy, very finely shredded newspaper. Mix 114g of this with 15 litres of water and a cup of wheat paste.
Mumbles - i have made 1.75" hemis using this method with a wall thickness of about 1/16", it depends on a lot of factors how thick the finished hemis come out i.e. suction rate of vac, number of holes in the mould, how much paper you have in the mulch etc. I am currently making a triple hemi mould for 1.25" hemis to see how small you can actually go while maintaining a wall thickness that isn't too thick. I'll let you know how it goes.
I hope this, along with mumbles post will help explain the process to non-passfire members!