What's the biggest reuseable filter with smallest pore size?

They can't be using these teeny filters, because customers can't wait that long.

Specialty coffee shops that offer 'pour-over' (drip) coffee definitely make coffee to order using small filters like the one you show (although in my area, they usually use paper filters). Customers are fine waiting the 2-4 minutes this takes.

For larger quantities, what a coffee shop might call 'batch brewing', larger filters such as these are commonly used:

These come in sizes ranging up to 12 cups, but might be tricky to find. Alternatively, you could experiment using one or more layers of cheesecloth, which is perhaps more easily available and scalable, although it might not filter as well as you'd like.

As a final note, I think your demand for pore sizes <10 micrometers might be a little too stringent. The filter you link to lists a .2mm mesh (i.e., 200 micrometers). I found this page with an analysis of the pore sizes in various coffee filtering products, if you're interested.

The key is probably prefiltering, combined with sedimentation. It's worth experimenting; you may not need all the steps. I've used a similar approach with a few different kitchen filtering needs (stock, brewing, jelly-making)

• You might even want to start with a colander with holes of several mm, but you're probably already doing this.

• Pass the broth through a very coarse sieve.

• Then through a finer sieve, or the coarse sieve lined with cheesecloth

• Allow it to settle for a couple of hours if possible (bearing in mind food safety, so probably in the fridge.

• Then pour as gently as possible* through your filter, leaving the sediment. To maximise yield, when most of the broth has passed through the filter, tip in the sediment and leave to drip slowly.

*In brewing you'd actually siphon the wine/beer off the lees (dead yeast) to avoid disturbing it by pouring.

You can try looking for a 10 micron sieve, which is definitely larger than a coffee filter, but may be a bit messier to work with. I did a quick Google search and came up with a bunch of relevant results.

Black pepper will make the clams purge the sand in mildly stirred ice cold water for about 20 mins. That's how we did it and was almost always more efficient.

Instead of what coffee shops use, i think you should be looking at what restaurants use. After all, the finest restaurants serve mussels, and can't afford them to be gritty.

The name for fine sieves/filters in restaurants is chinois. They are available in different fineness, you might have to hunt around restaurant stores and possibly also start lining with cheesecloth. Also, do look into the stepwise method suggested by ChrisH, with or without a chinois.