I wash it after sieving it to get some of the dust off, and to knock the smaller particles away if it was sieved while damp enough to be sticky. All it takes is a quick rinse/blast, so if you have a small sieve and a hose you can get everything set up and make a production line of it.

Perlite is really dusty. If you're using a gritty mix you need to get as many small particles out as possible, but if you're not then you can be a bit less stringent.

That MG stuff is too small, you really should try to find the coarse grade - it will make a HUGE difference in the aeration and water retention of your mix.

As for washing it - washing is not as important as screening. You really need to screen out the dust, after that, washing is sort of an option...it's beneficial but not totally necessary. I actually find it difficult to store, and just deal with in general, when its wet - so I don't bother.

One side note to that, if you are planning on planting anything that does not tolerate flouride well, you should go ahead and wash it.

PJ

The shipping is of course an issue/expense, but I thought I'd mention that Worm's Way sells the coarse perlite if you can't find it nearby.

I have never found any problem with finding it in large bags at Home Depot, very course and fairly dust free. I store mine slightly damp in 33 gallon plastic garbage cans. Al

Perlite tends to have a fair amount of fluoride in it, a compound to which many plants are sensitive to varying degrees. Rinsing it well reduces its fluoride content and eliminates fine particles that may or may not be a consideration, depending on the type of soil you might be making. For instance, I would screen and rinse it as a fraction of the gritty mix if I was using it as a substitute for granite or just including it in the mix for some reason, but wouldn't bother if I was using it in the 5:1:1 soil or something based on peat/coir/compost.

Al