basicly there are two ways of applying a finish. one way is in the wood so examples of that are applying dainish oil , tung oil or blopentine. rubbing in shelac , french polishing.
If you rub it in and keep doing it , it then fills the wood below the surface and you are left with a shiny surface ( no voids) these finishes tend to look better because it is a below the wood finish, it doesn't hide the grain.
whay I do is use dainish oil. the first coat soaks like a sponge I brush it on and leave it then wipe off a section at a time.
next I do the same thing. lots of dwell time allows moe penetration. the circular wiping is driving the oil into the fibers. i also dilute my dainish oil with about 50 percent turps, I wan tthe penetration, this hardens the surface of the floor prior to my topcoat of poly. fir is quite soft so I feel this is important.
next I do a third coat. with this coat I use fine wet or dry paper wet with the oil. I scrub the floor with that and that makes some sawdust suspended in the oil and then I rub it in again, circular patterns, followed by with the grain.
and then I do my poly..
so I guess this is what he is suggesting , you could collect dust from the job and use that. there are also different sealers that you might use, You could use shellac if you are doing a shellac floor, you can get sanding sealers. You can buy grain filler in a can for this purpose.
when you sand wood it opens the pores yes. when you apply water it raises the grain. the grain only raises once, unless you sand more. what is happening is the fivbers that were knocked flat by the sandpaper go to where they naturally want to be. this roughens the surface. You can then do a light sanding to knock them flat again but this sanding isnt' enough to make the fibers as distorted as they were before you raised the grain.
raising the grain is good habit in furniture refinishing. you dont' wan the grain to raise during finishing. If your coating is an oil based coating then it's not going to raise the grain when applied so you dont' really have to concern with it. If you use a water based finish, because it contains water it will raise the grain when applied. this isn't a good situation but it is a property of a water based finish. , so in that case I would suggest raising the grain with a damp cloth, then sanding smooth , before you use a water based finish. otherwise you have to depend on the coats of finish to level things out.
the more flat and filled the pores are before you start finishing the better it will look. Polyurethane can be applied so thick it can fill the grain , same with shellac or lacquer.. but it takes less coats if you have raised the grain , and filled the pores.
some use a pore filler , there is a technique where you put it on and use a credit card to scrape the surface off , then sand flat. or some use a burlap sack to burnish the finish.
the spiecies of wood is another factor, all my house is fir. but if your floors are of a different species how open the grin is varies. maple is famous for "blotching" so a sealer might be used to lessen the effect. if it is wood from knotty wood it will have more figure. one might want this "blotchy" effect you can apply stains to pronounce it. You might want that grain to jump out and be all different and see the beautiful character,, or you may want to build cabinets and really want them uniform.. some woods have open pores and some not, You can research the wood you are working with and compare as that can have a huge effect as well.
some woods react differently to different chemicals, they may have more tannins or different chemistry. a finish my father used and loved is nice mahogany finished with potassium permanganate.
https://en.wikipedia.org/wiki/Potassium_permanganatethis is a chemical reaction rather than a die or stain.. I believe it is also poisonous. he as taught to use it as a kid back in the early 40's by an old cabinetmaker that he apprenticed under.
some bury wood in barns to intentionally expose it to the animal urine and dung, again this affects the look,, not many doing that today but one could...
oak was often fumed with ammonia. it has a property where the ammonia fumes turn it dark, this was common when our houses were built and they would do things like install cabinetry and fumigate the house with ammonia, hard to make that fly nowadays, it's dangerous.
Burnishing flattens the fibers. You might put coats of finish down and burnish as part of the finishing steps.
If you use oil, the amount it soaks in depends a lot on dwell time of the first coat but also on the porosity of the wood. If you stop sanding at 100 grit and then apply oil you will get deeper penetration than if you sand to 120 and then use a 3M pad on the floor sander, that will burnish the wood. the absorption will affect the properties of the finish.
I like danish oil because it has some dryers and maybe a little poly and it's basically a lot like blopentine otherwise. I think they might add japan dryers to speed hardening. it still takes time to cure. these oil finished pop the grain and I like that usually,, but another thing to be aware of is while they pop the grain they also pop the flaws,, there are always some flaws unless you are perfect, I can see in my floor marks from the drum sander and from the edger, even faint bruises from the wheels on the edger. if you even drag your vacuum attachment on the wood you can leave lines.. You wont; see them until the oil gets on there. everything is a trade off. if your oil has a color and you rub it in you might also amplify damage, small un noticible cracks may show then as dark lines and become a lot more obvious. If you spray things on it may not collect in the cracks the same. so you can spray on a die rather than wiping a stain in for example.
I don't believe there are a lot of bad products but there is a lot of science and preference between different people and the choices affect price of materials , time spent, finish quality , the effects on "chatoyance"
I think if you talk to guys that come and finish your floors commercially they may try to promote "new and improved" water based products.. for our old floors I like oil better because they pop the grain and leave a more darkened appearance. the water based finishes are more clear, they don't darken the wood so much, they are way less stinky, it is faster the water based finishes dont; really promote the floor to darken with age, they may have UV blockers. My feeling is that oil based finishes play better in our old houses, but that's just my preference.. some may want light floors made of lighter woods and they may not want this darkening effect at all.
I remember speaking to someone who works with wood and says I hate oak! I thought well oak has some good qualitiues doesnt' it matter what you are using it for? I dont;l believe we should limit ourselves to the products but understanding them helps us make more educated choices.
guys doing it commercially want what is quick , they dont l want to show sanding imperfections, they dont; care if it pops the grain, they don't want to go over the floor sanding by hand, they have developed techniques that are much faster. they want to spend a day or two and get in and out and make their money and have happy customers. they don't want heavy fumes all day long every day. blame them ? I don't..
I spot filled the putty on the whole floor and used darker putty here because the wood is darker here ,, and didn't apply putty where not needed. a commercial finisher would probably use a filler that he squeegees out over the entire floor between standings. If we are renting sanders maybe that means another rental. they know their stuff so they are probably going to be better at operating their machines and have control over the system they have developed.. we learn as we go..
Mick and some others used that stuff you pretty much pour on and buff in and finished in way less time. His floor looks nice too. It seems to have dark pigments but there may be different colors. I'm not so familiar with this type of finish but it doesn't mean its bad or wrong. It would be interesting to know more about how it wears, does the product wear through? would it leave light spots where it wears? can it be recoated? does it leave a good protective coating? there is so much to know and so many chemicals that at first it is a lot to learn even to form decisions.
some choose to not sand and to restore the floor by rejuvenating the original shellac finish.. good point you save wood , if it is in pretty nice shape why sand them down. mine were too scraped up for that to work. they had already been sanded so since this is really the last sanding they can take I want a finish I can rebuild but I don't want to sand more.. I want a hard finish so they don't get scratched too much so I don't need to re-sand.. there are so many pro's and cons that there are a lot of choices and different angles to look at the decision from. some call in the pro's but they may sway you to the finishes they like. Most people have their favorites and when they develop a system they like they are inclined to stick with what they know. Professional finishers don't want to be experimenting with a lot of different products, they may even get discounts for volume buys. A professional finisher might be buying their products by the drum not by the bucket or gallon can. He might pay half what you have to so he's going to try to sway you his way naturally.
in a factory seting they may have more controlled conditions, so they may do it differently. some of the new pre finished flooring materials have alunimum oxide in the finish and that makes them hard wearing. this cant' be applied onsite because the alunimum oxide would sink to the bottom of the finish.. some shops have controled spray environments where they may use products that are more poisonous, they may have production spray equipment that can put a finish on more consistently than you or I could. a lot of newer products are UV cured so they may pass by UV lights to dry them that way. my dentist uses UV glues and hardens them with a fancy UV flashlight,, neat!