This thread is relevant to the Canon  CLI-42 OEM cartridges, but may have some relevance to other Canon catridges and in particular the CLI-8s.

For those of you who have been reading my thread on Purge cycles for the Pro-100S, you will know  my testing suggested there was about 3.5g (approx  3.5ml) of wasted ink left in the sponge when the printer reports the cart as empty.  The cart is usually thrown out at this point, unless you intend refilling with 3rd party ink.  The 3.5 figure is based on the assumption that the cart starts with 13ml of ink when full.

I came up with the crazy idea, for OEM users, of harvesting this wasted ink from 3 carts and refilling a 4th empty cart.  Since then I have determined that there must be even more ink in the sponge of the cart reported as empty.   In fact the figure is more like 4.26g.  I say this because I remembered Jose (Jtoolman) measured an empty cart he had been preparing to refill and he got it down to 13.58g.

So the simple maths:
Weight of new full cart = 27.33g
Weight of Virgin cart = 13.58g
Hence Total ink in a full cart is 27.33g – 13.58g = 13.75g   (Not 13g as had been assumed)

My Gray cart was reported empty at 17.84g.  Hence 17.84g – 13.58g = 4.26g left in sponge .

So percentage of ink left in sponge and typically thrown away is 30.98%.

I decided to do a simple test of how much ink can be extracted from an empty cart.  I did not want to start with an OEM cart so I used a 3rd party CLI-8 cart that was almost at the low ink level.  My guess is there was about 0.5g of ink in the compartment side of the cart.
I should have taken it down to the low level before starting, to be more accurate, but I figured the sponges are different to the OEM so accuracy was never going to be possible.  I just wanted to prove the concept.

The method of removing the ink was to use a plastic base clip which is intended to cover the exit hole and modify by inserting a shortened needle into the silicone washer seal.  The best way for you to see this is to look at the one made by Jtoolman on this video link: https://youtu.be/ACc0Bw5nicY

The same video mentions the virgin cart weight.  I did not even have to glue my clip like Jose did, because the needle was a tight fit through the silicon washer.  The syringe I used is quite big with a 22ml capacity.

The extraction went very well, taking only about 30s.  I slowly drew the syringe all the way out, which  brought a lot of air as well of course.  I then just waited a minute or so for the bubbles to disperse.  The 0.5g of ink that was in the tank remained until after I had pulled the syringe to it’s full extent, it then slowly moved into the sponge.  So a second attempt would probably have harvested some of that as well.

The amount harvested in just one single draw on the syringe was 3.97g.  Bear in mind that this cart was not reported as empty.  From testing my Pro-100 I know the low ink level is reported when there is about 5.22g left, which equates to 38% of the ink left.  So I think the ink yield is a satisfying result for just one quick draw on the syringe.

I also queried Jose about refilling a cart to 90%.  He agreed that that is at about the upper limit and that 80% was generally considered a good practice.

So here is a potential workflow:
1.   Stop using a cart when it gets down to 40% left (Not quite ink low level)
2.   When you have 2 stored empty carts, extract the ink from one (Donor)  and inject into the other (Recipient).  The Recipient cart needs to be reset and modified to allow refilling.
3.    When the next cart reaches 40%, remove it and replace with the Recipient cart.

One problem with this workflow is that it assumes 40% from both carts.  The donor cart will not yield 40%.  So the recipient cart  may only end up with say 75% instead of 80%.  However, I don’t think it’s an issue.  I believe what will happen is that when you first install the Recipient cart the printer driver will report 100%, due to the reset.  As ink is used it will drop gradually, but I assume at some point the prism in the cart will pick up that it has less ink than estimated by the usage and the ink level warnings will suddenly drop drastically.  It would be interesting to get some feedback on this assumption from seasoned re-fillers.

If it is an issue the options are to either not let the carts get as low as 40% or to use 2 donor carts instead of one.

The workflow is constructed, for the Canon Pro-100S in a way to avoid unnecessary purges of ink.  If you have the recipient cart ready when you take the current cart out to replace, and do the swap in less than 60s, there should be no purge.  The same applies to any cart swap, as long as the accumulated time a cart is out of the printer, since the last purge, does not exceed 60s, there should be no purge.

I currently have only one used OEM CLI-42 cart that has been removed from the printer.  In this case it was identified as empty by the printer driver.  Hence, it only contains about 31% of the original ink.  I will have to modify the workflow slightly for the first attempt.  eg.  I could take the next cart out at 50% full.


Bruce

I think it’s too risky to keep printing, even if the printer lets you.  Printheads are very expensive and the extra effort of transferring to another cartridge is not that big a deal once you got the few extra tools needed.  I certainly would not want to be weighing in-between every couple of prints because you only have 60s total accumulated time to have the cart out of the printer before a purge will result and ruin everything.  Measing the weight of 8 carts several times makes for a lot more work than transferring the ink.  You would also need to keep careful notes about each cart.


The cart I was drawing ink from was a 3rd party cart with a single sponge.  The OEM carts have 2 sponges, presumable with different densities.  So until we try the same method on an OEM cart it is difficult to know an answer to your question.  I note in Jose’s video he said there was about 5ml of water in the sponge and he also had the vent on top of the liquid chamber open.  I did not have the vent open.  Jose seemed to be getting just droplets.

Related to the fact that it was not an OEM cart that I tested, and I was having all sorts of problems with my Pro9000, which is where the carts came from, it is very likely the sponge has more ink than it should.  With the OEMs the ink tends to be mainly in the bottom sponge.  With these 3rd party carts the ink is well up the sponge.  It is very possible that I mistakenly thought I had a printhead issue when in fact it was a cartridge issue and in my attempt to fix a good printhead I burnt out the printhead as well.  I bought a replacement printhead but decided to buy the Pro100 before it arrived.

I am beginning to think I should just test the single "Empty" OEM cart I have and somehow store the ink until it is needed, just so I know this technique is worth pursuing. I will think on it.


That could work.  You may be interested in the gadget Jose discussed at the last Techie talk:
https://youtu.be/Ahstv2v64I0?t=1h12m35s



There is an air hole on the sponge side.  It is in a L shape and I believe it is sealed when the cart is packaged.  Removing the packaging unseals that vent.  I assumed that is where the air came from.  The other possibility is that I did not use glue on my modified plastic clip, so maybe there is a pressure leak there.


There are a lot of combinations of potential workflows.  The 2 simplest would appear to be to either remove the cart when the “Low Ink Warning” starts. ( ie.  38% left), or when the “Empty Warning” appears.  (ie. 31% left).  With the “Empty” option you could probably use 3 empty carts to get somewhere in the mid to high 80% area.  With the “Low” option, 2 carts are probably going to give somewhere in the low 70% area and 3 carts will result in more than you need, which means you have to hold on to that small amount of extra ink for a potentially long time.

Bruce

The 20% may at first seem disappointing, but a more logical way to look at this is that the 2.72g is better than 28% of the ink that is currently usable.
ie.  Only 9.49g of a cart is currently usable.

Bruce

When I cleaned the plastic clip after yesterdays effort I noticed it had started to come apart, since I had not used any glue like Jose had.
So I figured it was worth trying again, starting at the same place I left off yesterday.
Because of the vacuum formed in the cart, if you let go of the syringe handle it tried to go back-in part of the way.  So I tried a short pumping type action, by letting the syringe return a bit before I resumed.  It seemed to help.
So after the first attempt the cart weighed 15.04g.
I tried a jerking type action on the cart to force ink towards the exit port.  Not quite the slinging action suggested by Mike but should have a similar effect.
I connected the syringe again and used the same pumping action as before and weighed the cart to get a final result of 14.91g.

The total amount of ink recovered now is 2.96g, which represents a 31.1% increase in ink available.  Leaving 1.33g in the cart.
It's a cumbersome way to get the last few dregs, but it does indicate that there is potential if a better technique can be devised.
I was considering taking a purge unit out of an old printer and using it instead of a syringe.  Not sure how much pressure they can exert compared to a syringe.  Not everyone would have access to an old printer though.
I tend to keep them.  They may come in handy one day.
If the purge unit does work better than a syringe it may then be worth working on a solution based on commercially available parts.
Bruce 

Good question.  I meant to explain that earlier.  When I first took the cart out of the printer I taped the vent closed based on advise that if I ever intended using the cart in future for refilling, this stops the sponge drying out and rendering the cart unusable in future.  Although I think you can use rejuvenation fluid to bring it back to life, using the tape is the easiest option.

When I decided to try extracting ink, I decided to see what happens if I did it with the tape still in place.  If it did not work I could remove the tape and try again.
Seeing as it did work I never bothered trying it without the tape. When I tried drawing ink from the 3rd party cart there was no tape over the vent.  In that case there was a lot of air bubbles in the syringe.  In the taped off OEM case the bubbles tended not to form.

I will try to remove more ink out of the OEM cart with the tape off, but first want to glue the shortened syringe needle into the plastic clip.  Waiting for tomorrow, when ALDI have a special on Bondic Liquid Plastic Welder.

Bruce

That sounds interesting.  When I was researching the Purge units used in printers I found cases where home 3D printers had been used to make these types of pumps.

Further on my attempts to extract ink from an empty cart:
I tried gluing the shortened needle  to the plastic clip using the Bondic.  It uses UV light to cure the glue in about 4 seconds.  It did not work on this type of plastic, so I tried a hot glue gun and that did work.

After the previous test the cart weighed 15.12g without the sticky tape.
I removed the sticky tape covering the vent on the sponge side of the cart and pulled the syringe quickly to full length.  Nothing much happened, so I slowly closed the syringe and opened it quickly.  A small drop came out.  I repeated a further 4 times and weighed the cart.  It now weighed 14.77g without any sticky tape.

I then made a small homemade centrifuge by glueing a 1/4in bolt to a metal lid of a biscuit tin (about 8.5 inch or 21.5cm  diameter).  I taped the cart to the inner rim of the lid with the exit port facing out, put the bolt in a cordless drill and spun the cart for about 20s.  (No tape on sponge side vent).

I connected the cart back up with the extraction needle and repeated the previous method, but did it about 12 times.  The cart now weighs 14.6g, so ink extracted today is 15.12g – 14.6g = 0.55g.  I have to say it looks very small in the syringe.  I don’t know that the centrifuge achieved much.

The total ink now extracted is 17.84g – 14.6g = 3.24g.  Which represents an increase of usable ink by 29.3%.  Ink left in the sponge is 14.6g – 13.58g – 1.02g.

My thoughts at this point are that a small pump would do a better (quicker) job, because it’s taken several goes to get this far.

I have extracted a purge unit from an old printer and may play around with it on some 3rd party carts.

Bruce

Another thought.  I wonder how much ink you could get out if you cut open the top of the cart and pushed the sponge out by pushing a screwdriver into the exit hole to push it up and out of the cart.  Then (using rubber gloves), take the sponge and squeeze/fold it just enough to get the sponge INTO the large syringe.  Then push down on the syringe plunger to squeeze ink out of the sponge and out the tip of the syringe into a container?  This would only be worth the efffort based on how easy it is to cut off the top of the cart and deal with the "raw" sponge, plus getting the empty sponge back out of the syringe when done.  But might be an interesting experiment.

OK... just tore open a cart to see.  Turns out you can grab the little tab at the end of the cart and roll back the top:



It breaks when you get to the sponge part but you can stick a screwdriver under the sponge lid and pop that up too:



After rolling back that piece, the THREE sponges just drop out (pushed them through with a screwdriver):



I put all three in a big syringe and crushed them.  Didn't even get a drop of ink.  But this cart has been sitting around for a year with the sponge hole exposed.  It probably evaporated:



Anyway, interesting to see that there are three sponges in these carts and not two:

- A little "puck" at the exit hole
- A rectangular piece above that
- A piece with a different density at the top

Mike

Just an update on the use of a purge unit to extract ink from an empty OEM cart.

The purge unit I am using happens to be from a Canon MP540, which is a 5 ink multifunction printer.  It was not mine, someone was throwing it out and I grabbed it.  My preference would have been one of my old printers but I stripped them down last year so they took up less space and it appears I threw out all the purge units, because they tend to be messy.  The purge unit on the MP540 is buried deep inside the printer and I literally had to remove nearly every other module before I could get it out.

I started writing a description of a purge unit and decided it was way off topic.  Maybe I could start another thread.

The basic function of the purge unit that I was interested in using was it’s ability to pump ink.  It does this using a “Peristaltic Pump”, driven by a small electric motor.  I have attached 2 photos of the pump from the MP540; one with cover removed but drive gears still in place the second with the drive gears removed.  There is a tube where ink enters from the bottom left and exits to a waste ink pads on bottom right (see blue text).  The other tube ink enters top right and exits to waste pads on top left (see red text).

I could not find any technical details on the motor, other than a part number, so I assumed it was a 12V DC motor.  I also randomly selected polarity of power source, and got lucky.  If I had chosen the wrong polarity the purge unit performs a different function, so not a big deal.

I initially flushed some water through to clean out old ink.  Using the top (red marked) tube, I connected a third party empty cart to the IN side.  It was the same cart I used for the previous test on a 3rd party cart.  I had re-injected the recovered ink back into the cart.  Hence there was a small amount less ink than last time.  I also used the plastic clip with shortened needle glued into the base.  The tube that enters the pump is a very narrow rubber tube, which fits loosely into the needle inlet.  I wrapped some teflon tape around the tube to make it a tight fit.  After about 40s I had to stop because it had extracted 5ml of ink and I was not prepared for much more.  It definitely had more to offer.

I flushed the pump again and connected the OEM Grey cart that I had used in previous tests and has about 1g of ink left in the sponge.  I removed the sticky tape from over the sponge vent.  After 1.5min I stopped.  No ink had been extracted using the pump, or even entered the syringe/needle hub.  I reconnected the syringe and tried extracting ink.  In this case I did not extract ink but got a small quantity in the sringe/needle hub, which I just washed down the sink.

So in summary, the purge unit works but does not exert as much pressure as the syringe.

Bruce