There are two things you must do on a regular basis for analog tape decks (cassette or otherwise). These are cleaning and demagnetizing the heads and tape path. The second is far less important for cassette decks (multitrack or otherwise), and unless you move your deck around a lot or live near a place with a high magnetic anomaly in the earth, many people feel you can probably just forget about it (I'm not one of them, though).

Here's what you need, and since the Real Stuff isn't expensive at all (perhaps maybe it is in Chile), you should get good quality chemicals if possible. Don't worry too much about stocking up either, even a 2 oz. bottle should last years unless you're running a commercial studio or drinking the stuff (I personally recommended neither action).

I've standardized on TEAC/TASCAM chemicals perhaps because I've owned mostly TASCAM decks, but also because it's good quality stuff and readily available (Tech Spray brand may be easier to find on the net). I've found that TASCAM makes a nice set containing everything, model #TZ-261. Head cleaner and the fancy Q-tips are also generally available at Radio Shack, but rubber cleaner is a little harder to find, as is my Ultimate Tape Head Weapon. All you really need is the following:

• tape head cleaner (duh). In some cases, this is nothing but isopropyl or denatured alcohol. Most alcohol-containing head cleaners say in small print something like "safe on most plastics", which is Murphy's Law for "likely to disintegrate your 8-track multitrack front panel", so be careful with this stuff and don't spill it everywhere. Also, don't shubshitoot any other kindsh of alkohol becuz they mite have deleterererious effex on yore state of mind and they mite not bee good for your heds either... :-).
• rubber cleaner. The smell of this stuff is...overpowering, but it's the only thing safe to use on the pinch roller.
• tape head swabs. These look like, and essentially are, lintless, wood-handled Q-tips (TM I'm sure). The stuff sold in audio/electronics/recording/music stores generally have long sticks so you can get to nooks and crannies. This may be overkill (there's such a thing as too long) for most cassette decks though, but before you run off to the nearest medicine cabinet, remember the key word here is lintless. If little threads of cotton get everywhere you could be in big trouble. The absolute safest kind are the chamois types used for video tape recorders, which are expensive but feel so good...vegans will not approve however.

How to Clean Your Heads

• First, read your recorder's manual...the part where it tells you how to clean the heads!
• How often should you clean them? A good rule of thumb is after you finish a recording/mixing session...which gets the junk off while it's still fresh (well, it sounds good, anyway...I don't know if tape oxide actually "goes bad", but considering it's nothing but rust to start with, it's probably a good idea to get it the heck off your machine ASAP!) and makes sure that you're all ready for next time.
• Rewind to zero if necessary, and take out any tape you may happen to have in the machine.
• Moisten the swab with head cleaner and clean the metal tape guides and capstan or capstan shaft (the metal rod that touches the pinch roller). Don't push too hard on the rod or you will bend it. Also, make sure that there is not too much head cleaner on the swab when cleaning the capstan shaft, or it can drip down the rod directly into your motor, dissolving the lubricants in the motor. Guess what will happen then?
• Now that you have practiced  not pushing too hard on the swab, use a new swab (because the last one is dirty from the tape oxides on your guides), moisten it again, and carefully clean your heads (hint: the shiny metal ones are the expensive ones). There is also an erase head which is not so pretty to look at, but it should also be cleaned.
• Now get yet another swab (old Popeye cartoons are great fun while cleaning heads) and -- using the rubber cleaner this time -- clean your pinch roller.
• All done already? See, I told you it wasn't a big deal!
• One last thing...very important! Leave the cassette door open after cleaning so that the solvents can evaporate, and do not put a tape in until they do. Don't ask how I found this out, either.

Do Not Use

Do not under any conditions use the handy-dandy "head cleaning cassettes" that foolish consumers have demanded ("Duh...I can't use a Q-tip...it's too complicated!"). They operate by running a piece of fabric over your precious tape heads, that, viewed on a microscopic level, is very much like sandpaper. Then you get to choose  either the "dry" cleaning method (sandpaper a la carte) or the "wet" cleaning method (sandpaper a la mode).

What About Digital Tape?

DAT decks are entirely different, and for those I recommend you look up the DAT-heads site.

ADAT and DA-*8 decks are also entirely different, mainly because mechanically, they're really videotape recorders. So you should follow the manufacturers' recommendations with those, or anything else you think is better.

Here's a page which should be of great interest if you have any of the above digital decks.

The Ultimate Tape Head Weapon

I have had long debates with myself over the advisability of releasing this information to the public, but in the end...I won.

This substance was referred to obliquely in a book about recording I once found in a dusty shelf in the back of Electric Lady Studios, and at one time I actually found a bottle of it at a music store. I guiltily carried it off, knowing that I had found something akin to an original PAF pickup, and they didn't have a clue as to what it was really worth.

The bottle I acquired has a special "stealth" label printed in yellow on white so it literally cannot be read with the naked eye. However, using the blue filter on a pair of 3D glasses, I was able to read the inscription: "Teac Stainless Steel Polish SP-3".

It's a devilish combination of silicone and trichoro...no, I better not say the rest. But I will quote from the information on the back, which matches precisely what had been rumored in that book many years before:

"routine use will extend head life by polishing and filling molecular size pores in the crystalline structure of the head"

To the true cognoscenti, nothing more is necessary to say. Don't expect to find this magical liquid at the corner music store. You may have to go to a crossroads and make a deal with a tall stranger at midnight. It's been worth it, but the bottle is slowly getting empty...
-- Dragon