There are three ways I know of to clarify a stock. The goal of clarification is to remove the small particles that cloud the stock and make it opaque. First, the traditional method uses a combination of ground meat, egg whites, and small dice mirepoix. These are added to a stock and cooked to filter out the particles. This uses ingredients which can later be used to make a decent meatloaf. The downside is that you mess with the flavor of the stock, but not necessarily in a negative way. You can boost the flavor with the added vegetables and meat. Here is the result of my attempt at the traditional way:
Second, and third, are more modern methods which use the interesting property that gels will hold onto the particles and release their liquid in a process called syneresis. The result is a crystal clear stock (i.e. consomme). There are two increasingly well known methods for doing this. The first I tried uses agar-agar, a gelling agent derived from algae.
Agar clarification: Attempt 1.
500 ml white chicken stock
1.5 grams agar powder
1. Took 200 ml of stock and dispersed agar powder with a whisk.
2. Heated to 100 degrees centigrade.
3. Added in the remaining stock and mixed well.
4. Added to ice bath in a stainless steel bowl to set quickly.
5. After it was set, I whisked to break up the gel and promote syneresis.
6. Using a coffee filter, I extracted the liquid from the gel through a strainer. Coffee filters are said to be about 20 microns.
Notes: The stock is much clearer in post-clarification. Success mixed. It is a real pain to do this with coffee filters. I'll get a stronger material, and finer filter next time.
Gelatin clarification: Attempt 1.
To perform gelatin clarification, freeze your stock and then let it thaw through a cheesecloth or coffee filter in the fridge. The ice crystals do the work of breaking up the gel for you, releasing the liquid when it thaws.
You can see Jacques Pepin's grin through the stock! The downsides are twofold. First, you lose gelatin, and hence body. I'll either reduce this a great deal or add fresh gelatin back into the stock. Second, it takes a while for the stock to melt and drain: 1-2 days of valuable space in the fridge is lost.