On 1/31/20 11:48 AM, wrote:
On Friday, 31 January 2020 16:01:26 UTC, J-J wrote:

Ok, an update. Unfortunately, here's what happened after trying an oil
based ink from Staples. It almost seems like there was a "hemorrhage"
of sorts, then almost nothing (in fact, I didn't even realize there was
any trace at all until uploading the photo... I did turn the drum a day
ahead to get past the huge ink spot):

https://imgur.com/a/GcYaO8c

So, I guess it boils down to the incorrect ink, incorrect paper, or
both. For the chart, I printed my own on standard 8.5x14 printer/
typing paper. I did back the paper with two pieces of packing tape just
in case a spot like the one shown appeared so at least it wouldn't stain
the drum.

I'm just not going to be able to get away with testing this thing for
under $10, am I?

If you're willing to experiment. I gave you a clay-free rubber stamp ink formula that costs nothing to make. I've not tried it in your app.


NT


Yes, I guess you did. Unfortunately, I don't think I have any of that
stuff on hand. All I might be able to obtain is mineral oil later
today. Maybe I could try mixing a drop of that with the ink?

Well, the good news is that a VERY thin trace was made over a one day
period using nothing other than the Staples oil based ink and my packing
taped backed printer paper. Enough of a trace with falling barometric
pressure that I could see that the barograph at least works. I would
still like to get week's trace out of it though. I suspect the paper
I've devised isn't very absorbent, so any cheap modifications I could
try in a pinch would be welcome. Perhaps doubling (or tripling) up the
sheets next time around?