Wheel filters are the best way to filter any solution, this guide is designed primarily for people who want to inject pills, but safe is best when it comes to putting anything in your body, I highly recommend using these if you have to use at all. Learn from my experience.
Almost all needle exchange programs have them handy, in varying specifications of course. Wheel filters look like flying saucers and contain gauze which is capable of removing vary fine particles. They come in a variety of sizes, designed to filter specific particles such as chalk or wax. Although it is always better to filter a solution than not, cotton wool and tampons only filter down to about 50 microns, which can still allow particles to enter the bloodstream.
Green wheels contain 0.8 supor membrane gauze and are best used with hot M.S. Contin mixes. Blue wheels contain 0.2 supor membrane gauze and are best used to filter liquid methadone, or mixes of speed/coke/heroin from bacteria. Some users report they also work well with subutex. Blue wheels are capable of filtering bacteria, which means they are great for people with a lowered immune system (or indeed anyone who wants a super pure taste), however they don’t filter viruses (such as hep c or HIV). Red wheels contain 0.45 supor membrane gauze and are best used with chalky pills such as anamorph or physeptone.
Wheel filters are a bit tricky to master at first, but once you have the hang of them, they’re easy to use and your veins will thank you!!
When you’re using a wheel filter, you need to be patient and keep a steady hand. I always use a clean plate underneath my mix whilst I’m preparing it to minimize the risk of an unhappy accident. Wheel filters work best with 5ml or 10ml barrels. If you use a smaller barrel, such as a 3ml, the equipment has a greater tendency to ‘explode’ when you apply pressure. You should use firm pressure, but not try to force the solution through the filter. If the solution is not going through the filter, you may need to change filters or add more water to the mix.
Remember that wheel filters can only be used to filter solution in one direction. This means that you can either draw the liquid up through the filter or push it through the filter.
To use a wheel filter most efficiently you need firstly to wet the filter. Wetting a wheel filter removes the air bubbles and to decreases the chances of the filter blocking up.
Attach a clean barrel containing 2 or 3 ml of sterile water to the wheel filter. (You will notice that on either side of the wheel filter are two places to attach a tip and barrel. The tip ‘screws’ in, whilst the barrel is simply inserted and should fit snugly.)
sourced from "Network Against Prohibition" Filtering and Injecting.