I see that plate cleaning seems to become a thing here now with everyone getting exited…
Below is just for those new to all this, the veterans can just skip or ignore the lot.
Read if you want to, otherwise skip it
Do NOT put your plate in the dishwasher as tempting is might be!!
The steel of the plate will corrode badly in there.
Ok, that’s only the bit around the plate and you could use paint or ignore the rusting and crumbling over time…
But there is dishwashing tablets with great cleaning powers, great enough to wreck our quite chemical resistant plates.
For PEI it seems to work exceptionally well, the prints stick better than ever before, even without glue…
Until you realise the chemicals in those tablets are slowing eating away the top coating…
Do NOT use certain solvents for the cleaning…
Solvents like water, alcohol or baby oil (will explain that one if need be, so ask) are ok.
Stay away from things like acetone, MEK, degreaser or worse.
It might be tempting to remove some stuck bits of filament with a solvent able to soften it but chances are it will also wreck your plate.
Our plates, no matter the type or style are designed to NOT bond with our filaments.
So pay attention to their max temps and whether or not plastics like Nylon might be exempt as they might fuse to the plate.
A glue stick can provide an additional layer of protection to let you print those filaments anyway but you need to know what’s possible and how.
The only thing you need to clean the plate is something able to break the adhesion of the contaminant and to either bind to it (soap) or remove it (sponge, cloth, brush,…).
Alcohol has a very high creep factor, IPA and Ethanol both work but IPA is preferred by most people as it comes without things preventing abuse, like bittering agents.
Those additives to cleaning Ethanol can often leave a residue - try it on a clean window or mirror 
Not a problem if you go over the plate with window cleaner but can be a nightmare if left on the plate.
So alcohol is able to lift stuck things and residue…
It is also able to dissolve a lot of the contaminants you might add to the plate while handling it with your bare hands.
Keep in mind that even getting your wrist on the plate when trying to get a print of can leave things behind…
But dissolving also means it is NOT gone, it stays in solution.
So if the alcohol evaporates on the plate whatever was dissolved in it will be on your plate as well.
Hence the need to repeat this at least twice and with a new paper towel and fresh alcohol…
What about soap as the magical cleaning agent ?
Unlike solvents like alcohol, soap does not dissolve anything we care about, only the water does.
But the soap molecule binds on one side with a water molecule and on the other side with dirt, grime and some types of oil and grease.
So once you rise it off it all comes off - at least what the soap and you manual labour was able to.
Certain filaments do leave a residue on the plate.
I notice this most with matte and silk PLA filaments but also with some blends of PETG.
Without glue on the plate these residues can build up in areas where new prints overlap old ones or cover them.
Removing these once prints with other materials start to fail can be a true pain.
That’s one reason why I keep using the liquid on the textured PEI plate all the time.
IF you have a meaningful build up and something goes wrong with the print of a filament that has a strong bond to the plate it might mean it fuses to the residue on the plate.
Can happen very easy >
First layer fails so you increase the bed temp.
Got a bit better but still curls up on the corners, so you go higher still…
How to remove print residues once soap, IPA and window cleaner failed ?
Before you try any of what comes next:
Check you plate in the sun with clear skies or against a good light source.
Do you see a residue or do you see the top coat failing ?
Plates are consumables!
Fine cracks or flake like looking areas indicate damage.
No cleaning, no polishing will fix this.
Last resort measures…
Can’t get that print off, not even after putting it in the freezer over night?
Got it off but the base is still on the plate?
Cleaned what you can but those blobs, dots, lines and what not just won’t come off?
If you did not use brute force and ended up scratching or otherwise damaging the plate this might save your plate:
In case the print is still on it use a hot wire or fine teethed saw to cut it off close to the plate without damaging the plate.
Alcohol is more powerful than what you might think and our filaments are more scared by it than what their datasheets say.
I have a LDPE zipper bag, meant to keep your phone and other vital things safe in case you go over board and land in the drink…
A plate fits in it nicely and the zipper is air tight.
I use a special mix but equal amounts of IPA and ethanol from the hardware store will do.
Use a bag or suitable container to put your plate in and submerge it.
Cover properly or seal the bag and leave it alone for a day or two.
Do not rush things and have a spare plate at hand…
If there is a thick enough bit of plastic left on the plate (or you added a piece for reference) you will see how it might turn a bit pale depending on the colour.
A bit later the plastic looks as it has a thing layer of mould on it.
Then it starts to swell…
At this point your patience will be tested…
It IS tempting to now try to rub the stuff off.
Keep in mind though that this effect has to go all the way through and has to act on all that’s stuck on the plate, not just those bits on top of it.
Unless the plastic bonded to the plate gets soft as well you only get the rest off.
Use a toothbrush or similar brush of larger size but nothing abrasive…
Once all is off you plate is badly contaminated with the dissolved stuff.
Means you need to clean it fresh alcohol and clean cloths a few times.
What’s my soaking mix in case the plate seems wrecked?
25% IPA, 25% Ethanol, 45% Methanol, 5% of Ammonia solution at 30% concentration.
Not for the faint of heart and proper PPE while doing it all outside with a fresh breeze is a must.
No chance doing it indoors as the ammonia stink will be INTENSE.
I use a respirator with an activated carbon filter while dealing with the ammonia solution and until all is sealed up - again once taking the plate out.
Trust me when I say that you learned your lesson once you got a good whiff of proper strength ammonia…
The ammonia forms new and quite nasty molecules with the alcohols.
Key is of course to only have a very limited source of ammonia in the solution.
Enough to provide some of these aggressive chemicals but not enough have free ammonia left in the solution.
Means it takes a few minutes and requires some agitation to mix properly.
The effect is not really that intense but the ammonia does help to attack those stuck residues and plastics.
Downside is of course that it also attacks the steel of the plate some degree.
It won’t eat it up and corrode it like other chemicals or acids would but still.
The plate surface also has to be considered here.
Ammonia and what is creates with alcohol is powerful, sometimes too powerful for the coating on the plate.
I have not experienced issues with PEI but I avoid adding ammonia when dealing with effect plates or my TK99 plate - not that I ever had issues with the TK99 in terms of cleaning it or prints not getting off…