HP Photosmart A310 - Over-printing on photostock.

[ChrisGreaves]

FYI:
The printer is a tiny "HP Photosmart A310", comes with a HP camera via the shopping channel. nice enough unit.
I had powered-off too soon while printing a photo:

PhotoAsPostcard_HPIM2362 (Small).JPG

I decided to have a shot at printing a greeting message (in the fortuitous white space) using the photo printer.
I figured to use the laser printer to print a mailing address on the non-gloss side.
Waste-not-want-not eh?

When I fed the paper in in the direction of the arrow - date-stamp end first - the HP310 refused to print "Wrong paper size or type" or words to that effect.
When I fed the paper in "white" end first, the HPA310 printed as desired.

HPIM2365 (Small).JPG

My guess is that the HP3190 has a sensor that detects "none-white" at the incoming edge, but only for the leading edge (what else could it sense?!!???).
It can't be testing the chemical change in the paper, since the plain end fed quite happily.

[Leif]

FWIW, my HP CP3505 (colour laser) will often detect printing - particularly colour - on the reverse side when I re-use paper and print at about half-speed. I can only put that down to a sensor detecting, as you say, 'non-white' paper

[ChrisGreaves]

FWIW, my HP CP3505 (colour laser) will often detect printing - particularly colour - on the reverse side ...

But Cnet says "This unit also supports duplex printing, which allows you to print on both sides of a page in a single pass", so is your slow-down during regular double-sided printing, or is the slow-down when you are asking for single-sided printing but using "scrap" paper for the job?

[Leif]

Double-sided printing is always at a (similar) slower speed - I assume because the first pass is through a different path which is not of the 'high-speed' variety.

(It appears to be a very smart printer, printing the second side of one sheet while printing the first side of the following sheet. So although the paper speed is slower, it's printing twice as much. Or something.)

[ChrisGreaves]

... will often detect printing - particularly color - on the reverse side when I re-use paper ...

So this is something different. This is not slow speed "because I'm doing something with the first side of the next sheet".
It's as if the detection of color (on one side) sends a signal that "we must be doing double-sided, because the other side is colored, so slow down to accommodate processing time of the first side on the next sheet".
I have not expressed that very well.

If you wanted to design a printer that modified its speed to optimize double-sided printing, you'd need to know if you were printing double-sided. I would have assumed that a command from the end-user computer would do that, but perhaps they decided to trust their own hardware (more reliable) than depending on a computer (less reliable), and so based the switch/flag on the paper in the tray.

That would make some sense.

[Leif]

It's as if the detection of color (on one side) sends a signal that "we must be doing double-sided, because the other side is colored, so slow down to accommodate processing time of the first side on the next sheet".

But it knows it's not doing double sided! I'm more inclined to think that it assumes the reverse side has been pre-printed for good reason, and slows down so as to not leave rubber tyre marks on the other side

[ChrisGreaves]

... and slows down so as to not leave rubber tyre marks on the other side

As clear a case as ever I've seen of "Feuilles brush in where angles smear the tread".
I hereby nominate myself for the 5- award, multi-lingual division.