Many online resources claim that once you use "normal" ink in an inkjet printer, the printer is tainted and can no longer be safely used for edible printing. However, one edible ink vendor's maintenance guide actually recommends using Canon OEM ink when cleaning/unclogging the print head, then switching back to the edible ink cartridges for edible ink printing:
Please use the ORIGINAL Canon inks for cleanings, etc. as they are NON-TOXIC and will NOT CONTAMINATE your printer or print jobs!!! Also, if the printer is not going to be used for a while, please make sure to at least send a NOZZLE check to the printer once a week or more
if you like, to keep the ink free‐flowing.Once you've done the distilled water cleaning and placed the
Print‐Head back into the printer, do a thorough deep cleaning with the
original inks and do a nozzle check. If all looks good,then replace
with the edible ones and you should be good to go.
If the Canon ink is truly non-toxic, why not just use that for edible printing?
Edit: I found an article which suggests drinking normal non-toxic ink "can make you sick, but it is not life threatening." However, the article's only cited reference about inkjet ink makes a contrary claim, "Regular printer ink is toxic if ingested." Even if the normal ink can make you sick in large quantities, I still wonder how likely it is that the trace amounts used for an image on a cake are sufficient to make anyone sick.
Update: after looking at a couple MSDS sheets for Canon inks, I contacted Canon directly and this was their response:
Thank you for contacting Canon product support. I understand that you
are trying to use Canon inks for edible ink printing.Canon inks cannot be used for edible ink printing and cannot be
consumed.In addition, Canon does not recommend the use of edible ink or icing
sheets for use in any of its range of Bubble Jet Printers. The
printers are not designed to print with edible inks or to be used with
edible icing paper.Canon has not approved or tested edible inks or icing sheets.
Standard inks (either Canon manufactured inks or other third party
inks) are not safe to digest and immediate medical advice should be
sought if this were to happen.If the use of such inks or media were contemplated then extreme
caution should be taken to avoid cross contamination with the standard
inks and to avoid contact with any of the printer internal components
that could contain substances, which may be transferred onto the icing
sheet.In addition to the potential health and safety aspects, the use of
these edible inks or icing sheets in your printer could result in
reduced print quality, clogging of the printer's system or even damage
to the printer's components. Under these circumstances if a failure
develops in the printer, which is directly attributed to the use of
such consumables, Canon reserves the right to refuse to repair the
printer under warranty (in accordance with the applicable warranty
terms).I hope this information is helpful to you. Please let us know if we
can be of any further assistance.
Best Answer
I imagine there is a difference between ink that is designed not to harm you if you eat it and ink that is designed to be eaten.
With non-toxic ink, you don't care at all about the taste, and not many people are going to be eating it in volume (The dose is the poison). With edible ink, you don't want your cake to taste horrible, and people are going to be eating it all the time, so the safety standards are much higher.
You might be able to get away with using the non-edible ink, but frankly, I wouldn't try it.