Inking of cels is always on top?

[Fiore]

I learned that inking was always done on top of the cel and painting was done on the other side of the cel....but can both ink and paint be done on one side?

I bring this up because I was experimenting with inks on acetate and noticed how vulnerable it is to scratching. How can most cels look like the ink isn’t sitting on top? I know that most studios would xerox the lines in and then ink the imperfect lines on top that didn’t print well. (I know it’s kinda common to see some fine paint lines on top side to help artist know where to do shading/color ends when flipping to paint other side.)
So...I took one of my cheap cels and did a micro scratch test on the inked line on the front of the cel. It did not flake off on the front side. So I then did the same on the other side. To my surprise the ink line did flake off.;;; I’m so confused yo. (Unless they xerox the lines on the backside? Maybe it was a mistake of the studio and they just didn’t have time or money to fix the problem if they used xerox machine? Or maybe the color artist got so confused as to which side they were supposed to paint lol.)

So many questions, sorry! I was just surprised by this.XD
Does anyone else own a Cel that is both painted and inked on same side?

[sensei]

Most cels have the trace lines on the same side as the painting. This is done by sandwiching a carbon layer between the douga and the blank acetate sheet and running it through a machine that copies the douga in reverse on the back of the cel. Then the cel painter does a "paint by numbers" job by filling in the spaces between the trace lines. At some stage, some of these lines are reinforced (or sometimes added) on the front, but most of the outlining is on the back, often completely encased by the cel paint. Some paints are chemically more active than others, which is why oranges and browns, in particular, will "eat" or severely fade trace lines.

You can see the making of the trace lines on the cel from the douga on this little video made to illustrate how Sailor Moon was animated. Watch carefully at 1:17 and you'll see the carbon sheet being sandwiched between the douga and the cel sheet, then passed through the printing machine. (Other interesting things get illustrated, like the way cels are loaded onto the light table and photographed, but it skips the whole process between the storyboard and the douga, including interesting stages like the layout, rough, genga, and shuusei.)

[Fiore]

This was helpful thank you! And here I thought most cels were just inked on top and not same side. I guess the really older type of cels did the separate method before the xerox came along?

[sensei]

Yes, Mushi Pro was one of the studios that did hand inking long after others had gone to the cheaper and quicker photocopy process. Also Sanrio: The Sea Prince and the Fire Child (1981) was all gloriously inked by hand, and so while many cels from the 90s look old because of line fading, the ones from this anime film look like they were made yesterday.

[Fiore]

Also Sanrio: The Sea Prince and the Fire Child (1981) was all gloriously inked by hand, and so while many cels from the 90s look old because of line fading, the ones from this anime film look like they were made yesterday.

That’s pretty impressive for the studio to keep hand inking even though xerox was there.

I had to look at your The Sea Prince and Fire Child pieces again. If the ink done traditional look like it was made yesterday even today, then that’s great info to know. Thank you so much Sensei!
(Definitely gotta look out for this series on auctions. It would be really neat to see the difference between cels in person.<3)