George, there are several cleaning methods other than HWE
I'll mention some common ones
CCing methods 101;
There's Host cleaning
essentially, solvent soaked ground corn cobs that are thrown on the carpet, ground in with a counter rotating cylinder brush machine (
CRB) and then vacced up.
Then there's "dry" foam
(a silly marketing ploy, cause "foam" ain't "dry")
Von Schrader champions that method.
It's a shampoo foam generating machine with a cylinder brush that agitates the shampoo than a vac picks some of the suds up
Then there's scrub'n run sCampoo method.
Commonly called encRapsulation.
i didn't call it "cleaning" cause no soil is actually removed.
What you do is, scrub in a shampoo with pixie dust additive, swirl it around and call it good.
However, It does improve the appearance of carpets to greater or lesser extent, depending on soil load and type soil.
NOW I'll get to OP.
Bonnet/pad cleaning and OP cleaning are absorbent pad cleaning.
Bonnets of either synthetic, cotton or blends are used under a rotary or OP machine to "spray'n wipe" the carpets clean.
OP stands for "oscillating pad".
Instead of going round and round, like a rotary, they have an oscillating movement to them.
Best I could describe it, it's like a BIG dual action sander or car wax buffer.
..L.T.A.