What happens if you don't clean your guitar?
You may have heard of some famous players who never clean their guitars and are totally okay with that.
What would happen if you never cleaned your guitar? I'll tell you.
Before I tell you, a question answered:
What guitars can withstand not being cleaned the most?
As for why those very specific guitars can handle the dirt and grime the most, there are three main reasons.
Reason 1: Poly everywhere. Both the body and neck are coated either in polyurethane or polyester. This is a totally over-engineered way of finishing a guitar. Finish types like this will dull but never check (as in not crack nor peel nor chip on their own).
Reason 2: Sealed neck. The 1-piece maple neck on a Squier has a rather thick coating of poly on both the front and back. It will never turn gray nor turn green, and as just mentioned, it's an over-engineered finish. In addition, the sealant on the maple can withstand an absolutely ridiculous amount of gunk and grime and still be playable whereas rosewood cannot.
Reason 3: No vibrato system. Less moving parts = longer lasting instrument.
Now as for Fender guitars, the bodies will last but the 1-piece maple option won't. The coating used on the back is a satin urethane and the front coating is a by-design (due to player demand) thinner coat. Of what, specifically? That I don't know, but it is a decidedly thinner sealant compared to a Squier neck.
What happens on Fender 1-piece maple necks is that you start to see staining on the fingerboard after a while. And yes, that is totally normal. It may take a few years or a few decades depending on how much the guitar is played, but it will happen. It is considered a good thing and a cool look when a maple fingerboard stains these days due to player wear.
How often do I clean guitars I play regularly?
Not that often, to be honest.
I play Jazzmaster guitars, and presently they all (regardless of model) come with maple necks that have rosewood fingerboards.
Ordinarily, I will give the guitar a dry wipe-down with a polish cloth and that's pretty much all that's needed. On the Squier Jazzmaster, the body is polyurethane coated, so when it starts getting seriously full of gunk, I just use paper towels and Windex.
Does paper towels and Windex scratch the finish? Yes, it will make tiny scratches. Do I care? No. All I'll looking to do with a wet wash is to clear the gunk. Windex is safe to use on poly finishes and doesn't harm the plastic pick guard, knobs, switchgear or any metal components.
I don't bother cleaning the fingerboard unless it really needs it. And I rarely clean the back of the neck, because every time I do, I have to re-work my finger oils into the neck just to get it feeling right again.
Now when it comes to nitrocellulose lacquer finish guitars, I treat that very differently compared to poly.
I rarely wet-wash nitro because the damn stuff scratches so easily. The easiest nitro-safe stuff is Virtuoso cleaner and polish. Other guys use carnauba wax because it's safe on nitro (on that link you'll see a few options for Meguiar's brand, which seems to be the go-to choice for guys that use this stuff on guitar finishes).
My way of wet-washing nitro is using a lightly damp polish cloth that has water misted on to it from a spray bottle. True, this does not bring out the best shine, but it is safe for use on the finish and scratches it the least. Otherwise, I just dry-wipe using a soft polish cloth and that pretty much works.
To note, there is absolutely no damned way to clean nitro without scratching it. It will scratch, it's gonna happen and there's nothing you can do about it other than minimize the effect as much as you can until the finish starts checking (where at that point you don't care about scratches since the checking looks cool).
What happens if you clean nothing on an electric guitar?
If all you ever do is change the strings and never clean the instrument, this is what happens.
Whether poly or nitro, gunk will appear, mostly in the forearm area since that's where you physically touch the instrument most. For really filthy guitars a "dirt stripe" may appear in that forearm area.
Pick guard (if exists)
No matter what color it is, it will become full of gunk and look nasty, but that's about it.
The worst that can happen here is that the adjustment height screws tarnish, then rust, then have gunk caked on over that rust, possibly making them unusable.
The bridge itself will work fine, but if you have saddles with individual screws for height adjustment (such as on Strats and Teles), those screws will, like the pickup screws, tarnish, rust, get caked up with gunk and possibly become unusable.
Knobs and switchgear
Gunk will get into these and eventually cause a "scratchy" sound and/or stop working properly.
In the worst case scenario, you'll see green (yes, as in mold) frets on the "dusty end" of the neck.
On sealed maple you'll see green/gray crud pile up. On rosewood it's the same but worse because you're pushing that gunk into the open grain every time you play the guitar.
The worst that happens here is that the slots get clogged up with crud and will cause tuning instability eventually.
Nothing really much happens here. Tuners that never get cleaned really don't perform any worse than ones that get cleaned regularly. What makes a tuner fail is if the lubrication dries up on the gears, which ordinarily happens just from it not being used for an extended period of time.
How do you clean a really, really filthy guitar?
If the guitar is vintage and has nitro on it, use the Virtuoso stuff mentioned above for the body and neck.
If the guitar has poly on both the body and neck, how you clean it is as follows:
To do an absolute top-to-bottom cleaning for a guitar that's been really neglected, the best option is to slowly take the whole thing apart because there's probably years of gunk hiding everywhere.
Using a Squier Strat as an example, what I would personally do is take off the strings and dismantle most of the guitar. I'd leave the tuners installed and leave the electronics installed in the pick guard, but everything else comes off - including the neck itself.
I know I would find gunk where the bridge sat, under the pick guard, under the plate in the back and in the neck pocket area, so I'd just clean all that as best I could.
If the guitar had one of those really grimy necks with green frets and loads of gunk on the fingerboard, my way of cleaning would depend on fingerboard material.
If the neck was 1-piece sealed maple, I'd run over it with a toothbrush (yes, the poly coat on the maple can totally handle it) and Windex, then polish the frets after that with 0000 steel wool, being sure to avoid hitting the wood with it while polishing. The 0000 is the lightest grade there is and basically feels like cloth. I'd use that specifically to take off the least amount of metal from the fret wire.
If the neck had a rosewood fingerboard, I'd have to tackle that differently. I'd be dealing with an open grain slab of wood with gunk buried deep in it.
What some recommend to attempt to remove grime from a rosewood board is the use of 0000 steel wool. The board is lightly rubbed dry to remove the worst of the grime, then a light coat of fingerboard oil is applied afterward. The recommended stuff to use is Gerlitz Guitar Honey.
To some, it seems to make more sense to use a mild degreaser (such as a diluted solution of Dawn dish soap and water) to get grime off rosewood, but you run the risk of sealing the wood when you do that - even if just using plain soapy water. Remember, a rosewood fingerboard is an open grain slab of wood. While it's perfectly fine to tackle maple with pretty much anything because it's sealed, rosewood isn't so it has to be handled differently.
As for the guitar nut, Windex and dental floss cleans that up pretty good.
Concerning plastics, Windex and paper towels.
Concerning metal components (bridge, knobs and tuners), again, Windex and paper towels.
Your biggest annoyance would be the rosewood fretboard because of the open grain nature of it. That and the frets since you have to polish those one by one using the steel wool (I suggest taping up the wood so you don't hit it when polishing). But for the rest, Windex and paper towels works just fine since it's all poly coated, plastic or metal.
Can you get mirror-like shine back from a poly-coated guitar body?
This is a bit of a loaded question because it depends how heavy or light the guitar manufacturer sprayed on the poly coat originally.
In theory, you should be able to simply buff a poly body to a mirror-like shine using just about any cheap buffer...
...but I honestly would not bother simply for the reason it will be insanely difficult buffing the entire body.
At best, you will be able to get only the front and back of the body back to a mirror-like shine again. But as for where the neck pocket curves are, eh... not really. You're free to try if you want, but it probably won't work.
It is actually easier to purposely create a "uniform dulling" of the finish. How? With the 0000 steel wool. Instead of attempting to recreate a mirror-like shine, you're going in the complete opposite direction and creating a uniform dull gloss.
What's the advantage of doing this? Better to have a uniform look across the body than to have one part dulled, one part shiny, one part sorta-shiny and so on.
Uniform dulling is something you do by hand, so you will be able to "dull out" every single part of the body evenly. And being 0000 steel wool is so light, it is highly unlikely you'll break through the poly down to the paint.
Using the steel wool for uniform dulling isn't "relic'ing" the guitar. Rather, it's just a way of getting a poly finish to look even without refinishing the body.
Do you have to take everything out of the body before doing this? Yes. The neck has to come off and all the electronics taken out so you can do the job right.
In the end, you'll be left with an even look. A bit of a "weathered poly" look, so to speak. And yeah, it looks cool. More of a "woody" appearance overall, even on solid-color painted guitar bodies.
Is it safe to keep a dirty guitar?
This is The Big Question. And the answer is this:
Yes - if the guitar is played regularly.
What makes a guitar screw up and break faster than anything else is not playing it. A guitar that is played often operates just fine no matter how filthy it gets. It's when the guitar sits in a corner or in its case that it stands the most chance of being damaged.
Remember, guitars are machines. And machines run best when used regularly.