What is Perlite, and Does it Work?

Take note of an important edit to the post immediately previous to this one.  The edit is at the very beginning of that post.
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Even if you never buy a bag/box/carton of it, you'll see it in many or most bags of potting soil...even in the cheap ones.  It looks similar to bits of white styrofoam, but is totally different.  Styrofoam is a polystyrene synthetic plastic, a petrochemical.  Perlite (not a trade name) is a generic term for a certain group of natural, inorganic, volcanic silicates...they are a unique form of volcanic glass.  [Sand is a silicate, but is different from Perlite.]  After mining, the substance is heated in a manufacturing process and that causes it to expand greatly.  In that form, it can absorb water and later release it slowly.  It's both inert and sterile, and has no known toxicity or fire hazard.  There's no need to go into the chemistry of Perlite in great detail.  All we need to know is:  what are its functions in soil, and does it work properly?

The functions of Perlite in garden soil are as follows---
1.  It contributes to soil aeration by preventing (to some degree) soil compaction.  Every time you water your plants---especially those in containers---the soil compacts a bit.  That forces out the air; and remember, a good soil should be about 25% air.
2.  It helps retain water, and contributes to good drainage.

Does it work properly?  Is it any good?  Now we enter the world of opinion.  :)  I'm not aware of any scientific, controlled experiments that prove either of the propositions in the paragraph above.  There are, however, a ton of opinions on the matter.  Lots of anecdotal "evidence"...which may be right or may be wrong...or right only in some circumstances.

Many gardeners swear by Perlite; they love it.  Many others say it's mostly a useless substance.  Of those, the ones who like it just a tiny bit say that vermiculite is better.  [My observations here are based upon reading many, many online gardening discussions in a wide variety of venues or forums.]  Based on my own limited experience in this area, and on Logic, I thinks it works... and works well.  Take that for whatever you think it's worth.  In any case, I certainly wouldn't spend time picking it out of a bag of potting soil...and most bags have it in them.  As to buying a box of only Perlite and then adding it to my container soil, I would do that but am trying to garden on-the-cheap.

Happy Trails, and Be Well