How can people answer any of these questions with no knowledge of the product at all?
I have the Teac pink and blue or green rubber cleaners. NO they do not go bad.
The Pink solution was similar to if not exactly dry cleaning solution. It evaporates very quickly and we at Teac Factory Service in Chicago used Denatured alcohol when they learned that it worked just as well and did not have the O zone depleting nature of the pink hydrocarbon.
I seem to remember that the name was Trichlorotriflouroethane.
The blue color solution was made by Rawn in Wisconsin. It is 97% Naphtha which is what I use from the paint or hardware store myself. The blue color is photo reactive and if left in the sun it will turn green. That is the only change that will take place but the color is just there for looks.
The chemicals work the same right down to the last drop.
Now as to using Isopropyl alcohol. It does no good to use that on tape heads or rubber. It does not have the ability to dissolve oxides and the binders used with them. It is like using water on such products in that all you get off is from friction not the chemical.
Denatured alcohol is cheaper and does the job well and I have been using it for 45 years so far. It can be used on rubber for cleaning and in 45 years I have yet to see a pinch roller crack due to the use- most all these alcohol warnings are from people that repeat stories with no basis in fact.
So the stuff you paid a lot of money for like S721 is all a ridiculous profit making product for those who sell them. They are of no real use by the people that know what they are doing.
Denatured Alcohol for about $12 a gallon at Home Depot and Naphtha as well will get all the stuff you need to service tape deck.
On occasion I use Nu Finish Car polish for heads to polish off corrosion but it also leaves a surfactant that make for better tape to head contact.
I have proof of this as I have seen variations of audio level be cut in half just by the treatment of the nu Finish polish from the orange bottle.
The only place I use Isopropyl alcohol is on cuts or to clean PCB's after denatured. That is it. Rubbing alcohol from a medical store is all full of water perfumes and other junk. No one should be using any form of that stuff. It comes out of cheapness and stupidity that it is bought.
You kinda had my attention until you mentioned nuFinish.
Also denatured alcohol is not something I would EVER put on my tape deck heads...never mind the rubber roller...because it usually contains other chemical additives that can cause issues...acetone being the first one that comes to mind.
"Denatured alcohol is used as a solvent and as fuel for alcohol burners and camping stoves. Because of the diversity of industrial uses for denatured alcohol, hundreds of additives and denaturing methods have been used. The main additive has traditionally been 10% methanol, giving rise to the term 'methylated spirits'. Other typical additives include isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and denatonium."
The notion that you need some kind of strong chemical to dissolve the grit-n-grime off your heads and tape path, makes me wonder how often you clean your heads that they need that kind of attention?
Like I mentioned...I use 99.9% isopropyl alcohol...the industry standard for tape deck head cleaning. It breaks down any mild surface grime to be removed with gentle rubbing...and since it's almost pure isopropyl, there is no water, which is something you would NOT want on your metal parts...
...however, for cleaning the rubber roller, water is probably the safest thing to use...not any kind of alcohol, solvents or Naphtha...and again, if you need those kinds of chemicals to clean your rubber rollers...how much grime are you dealing with, anyway...?
Maybe you should avoid bad/old tapes with issues, and you won't have to clean as much.
I run 499, 911 and 468 on my 2" and my 1/4" decks...and I rarely see any kind of build-up of crud.
I said medical alcohol. That mostly is denatured alcohol.
Mmm...I don't think so...not with the weird variations in additives found in denatured alcohol from brand to brand.
Denatured alcohol has its uses in the wood shop and for cleaning purposes...but I don't think they use it in hospitals for medical purposes.
I think "medical grade" is associated with the alcohol percentage...and I think 70% and up qualifies.
Now there may be denatured alcohol without any additives for hospital use...but most of the stuff found at Home Depot has additives that are not appropriate for that purpose...or for putting on a tape deck head...but some people kinda hang their hat on the
"I've been using it for 40 years without problems" argument.
OK, keep using it then. I hope the acetone doesn't eat away any of the plastic on your erase head or other parts in and around the tape path.