Re: Rancid oil (Re: Ultrafine Clear Film and Epson 2200

On Fri, 22 Oct 2004, Christina Z. Anderson wrote:

> I know in the printmaking lab they use baby oil (which I think is just
> mineral oil with baby butt smell added) to oil paper negs. The exposure
> times with these in relation to transparencies is 6 1/2 mn vs 4 mn 15 secs
> approximately, on silkscreen (is this diazo?), so only a 50% increase in
> time. After a while my prof said they lose their transparency, so one needs
> to reoil. Apparently, from below, Katharine, you never reoil, so it is
> another myth?

As I described at some length in Post-Factory #8, "Paper Positive/Paper
Negative: goodbye paraffin, hello beeswax -- and some second thoughts
about oiling", a waxed and an oiled negative had exactly the same curve,
but there were crucial differences.

For instance, even the most even-fibered paper when paraffin waxed got
blotches and mottles one place or another. No matter how carefully I wiped
"I just managed to move them around." And all sorts of other troubles,
although by that time I was very skilled at waxing. I decided to oil
instead. Then,

"We know that oiled paper, wiped and let dry for a few hours, reads a lot
lighter on the densitometer than not-oiled. But when I happened to take a
reading a day later, darned if it wasn't denser again... ..the next day --
denser still.

"Then I remembered reading (in Post-Factory) that beeswax floods less than
paraffin. I tried it. It floods less. It looks good, even and smooth,
promising to lie flat for contacting [which the paraffined paper never
did] so paraffin is over. Get beeswax at craft stores & candle shops.

"[As for the oiling] By 6 weeks, oiled paper has dried a *lot* and...not
evenly. The darks increased opacity much more and the darkest darks the
most, except in some strips the midtones changed most...."

Then I went on to describe the various oils I'd tried, "I tested every oil
in town. Singer Sewing machine oil should be non-drying but acts the
same...castor oil is promising, very thick, takes 2 days to soak in, then
starts back up; mineral oil; peanut oil, corn oil; lemon furniture oil;
Vaseline takes a day to transparentize, then is the same, larch turpentine
much diluted is still too shiny, and all, *all,* soon start to dry. After
a week they seemed stabilized, but 6 weeks later showed drastic change.

"So for a quick & easy negative, do Canola oil & use within a week or so,
but don't count on next month. Of my samples, mineral oil was the worst,
very spotty viewed from the back; castor oil probably changed the least."

I note of course that those are generic terms.... just like pigment
colors. One maker's "mineral oil" may be very different from the next. And
I daresay those values will vary also according to the paper, I suspect
also according to how heavily the oil is applied in the first place. I
used a paper called Karma because, viewed on light table through a lupe,
it had the least mottling.

However I found that "Beeswaxed paper reads the same from day one, and so
far remains the same -- smooth, clear and touchable. Speckling is minimal,
in fact the wax seems to subdue texture....[However and meanwhile] Henk
Thijs reports that he uses the paper plain, no oil or wax. Exposure is
much longer, he says, but otherwise there's no difference."

JS.

> Paraffin and beeswax should not go rancid. I used to use those for bw print
> paper negs. But this requires an iron.
> Chris
>
>> My experience with rancidity is that it depends on the oil. The first
>> oil I used, a generic vegetable oil from the grocery store, turned
>> rancid, and no myth about it. I don't remember whether it was days or
>> weeks, but within a short time the negatives developed a distinct
>> rancid odor, which was pronounced enough to knock one backwards a bit
>> when opening the file box containing these negatives. This odor lingered
>> for a couple of years and then faded, but at the same time the odor
>> faded, the paper turned brown rendering the negatives useless as
>> negatives; a short time after beginning to turn brown they became
>> brittle and would fall to bits at a touch.
>>
>> At the first hint of rancidity, I cast about for a better oil and
>> settled on mineral oil; I have mineral-oiled negatives that are a
>> decade or more old and as fresh today as when they were new.
>>
>>
>> Katharine
>>
>
>
Received on Fri Oct 22 12:00:54 2004