When all other cleaning methods have failed...the last cleaning method to try.

[PeterBJ]

But you also want to unclog the print head. Hopefully the Chlorine bleach can do what no other chemical can do.

Chlorine bleach is deliberately made alkaline by adding sodium hydroxide, to minimize the risk of Chlorine gas formation if accidentally mixed with acids. apart from being corrosive, strong alkalines, especially if hot can break epoxy bonds and might so ruin the print head.

As stated by mikling bleach is the last resort and you should know the risk of ruining not only the print head, but the logic board as well.

 

[mikem65d]

OK so please forgive my ignorance, but are we talking about just regular 'ol bleach like Clorox or similar fabric wash products here?

 

[martin0reg]

By now I have not noticed or identified any fungus issue - but I have a R800 which I'm not able to declogg, even after soaking for a week and do the push and pull via syringe and tube on the inlet spike, the yellow channel misses 50% of the nozzles, not a single nozzle did come back.
So I tried the bleach:
1l bottle labeled "eau de javel", for washing and also cleaning, containig 2,4g hypochlorit per 100ml. Diluted 50% with aqua dest (dilutions for washing and cleaning are much higher) and put it on the soaking towel under the printhead, for one day.
No effect so far, yellow is still missing - but there is a smell of swimming pool in my room...

 

[The Hat]

@martin0reg try the bleach undiluted next time but be care how you hand it..

 

[martin0reg]

Another attempt of "last resort" with bleach, now in a canon printhead:

I am trying to reanimate two old s9000/i9100 which weren't used for more than 5 years. Stored with no precautions at all, almost all carts were empty but not totally dry, I was surprised that they printed some lines at all.
After cleaning cycles one printhead showed around 10% missing nozzles in all 6 channels. Soaking the head on pharmacist's amonnia solution won't make it better, the same missing nozzles persisted.
Ther was no sign of electrical damage, nozzle rows were looking fine under a strong loupe (...while most of my "clogged" canon printheads were showing already damaged nozzles..)

So I tried two methods for the first time:
- dripping a stronger amonnia solution on the outlet of the carts to let it sink into the sponge, then put it back in, make a cleaning cycle or even print a purge pattern with the amonnia soaked cart.
- dripping the solution directly on the nozzle plate after possitioning the head upside down on a dish.

My last resort now was dripping the bleach onto the nozzle plate... very carefully so that the puddle don't overflow, just sinking slowly into the nozzle rows.
I can't say for sure if it was the bleach - but after the last step the missing nozzles are back!

NOTE: The combination of amonnia and bleach seems to be more hazardous than each on his own!
I applied only drops...a few ml at the most of both fluids...

 

[stratman]

NOTE: The combination of amonnia and bleach seems to be more hazardous than each on his own!

Potential Poisonous Gas!

Never combine chlorine bleach and an ammonia.

 

[pharmacist]

Actually. Chlorine bleach with caustic ammonia will smell horrible, but the high pH ammonia keeps the the sodium hypochlorite stable. If you add acid to it, the hypochlorite will disintegrate into the free and dangerous chlorine gas. However: the combination will be awful, but not necessarily very dangerous, but still very irritating if inhaled. The worst combination would be chlorine bleach (sodium hypochlorite) with any strong acid, as this will release the dangerous free chlorine gas. Anyhow: don't mix at all and stay safe .

 

[martin0reg]

Thank you for emphasize the hazard notes.

One remark in mikling's initial posting seems to hold true for my attempts..

... Epson printheads will not take to bleach at all...it will be damaged by it. So far Canon printheads appear to be able to withstand bleach within the ink channel. I use the word appear because only 5 tests, all successful ,withstood bleach. So there is some inherent risk.

..the r800 is now totally blocked (and was sold as defect / for spare parts)
..while the canon head seems to be fine - until now...

 

[martin0reg]

Sadly the second printhead keeps a clogged yellow channel:
First it seems to be the better one of the two, all channels were looking good after cleaning with "normal" solution, except for yellow.
But this time there is no improvement with the bleach, the same identical nozzles (around 5% *) are blocked and won't come back, even after soaking overnight.

(* the nozzle check pattern of the s9000/i9100 shows a grid similar to epson, so you can identify single missing nozzles. Other than with newer canon printers, which nozzle checks are showing solid bars with more or less stripes)

 

[The Hat]

I also had a chance to try soaking a couple of my duff print head in bleach, after an over night dip and a good rinse in water none of them looked any better for this special treatment, they were for pigment use and not dye so I don’t know if that makes any difference.

A burned out nozzle will always stay a burned out nozzle even with the best intentions..