Fredrik-Rudy,
I liked pH because it was relatively easy to get comparative info with
simple litmus paper strips.
Roger brings up a good point regarding the refractometer.
I don't want you to put excessive attention to the base label material, but
do sincerely suggest that you look for ways to evaluate the surface for
change in release agents, surface finish, wetting angle etc. If that
surface is changing on you, everything else may be a waste of time.
I realize that 'it is only paper', but... [maybe it is Kapton, etc]
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
Sent: Wednesday, August 19, 2009 10:13 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning a little too much...
Fredrik:
If the pH measurement is a good predictor of whether the ink is attacked (as
I suspect it will be), this will not be the first time (nor, I am sure the
last) that chemistry vendors, and particularly cleaning chemistry vendors,
did not really understand the chemistry of what they were selling!
Rudy Sedlak
RD Chemical Company
--- On Wed, 8/19/09, Skillborg Fredrik <[log in to unmask]> wrote:
From: Skillborg Fredrik <[log in to unmask]>
Subject: Re: [TN] Cleaning a little too much...
To: [log in to unmask]
Date: Wednesday, August 19, 2009, 1:24 AM
Steven, Rudy,
Thanks for your support.
There should fall no shadow on Zestron, they've helped us out with
different tests, we've just not find a solution, yet...
At my previous employer we didn't clean before coating so I'm fairly new
to these kinds of problems.
Unfortunately the problem seems to have no correlation to humidity
changes over the year, we see this regardless of season.
The pH we don't measure, Zestron has told us that it's not the correct
way of maintaining the bath concentration.
I will test with a solution I made two weeks ago. It might have absorbed
enough co2 to function well.
Also I'll start to measure pH with fresh, old and 50% fresh solution to
see if there is any difference.
Thanks again.
// Fredrik
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: den 18 augusti 2009 15:24
To: [log in to unmask]
Subject: Re: [TN] Cleaning a little too much...
Fredrik,
I wished to lend a bit of moral support and ask a question or two.
I've always found that Zestron-US was quick to help me out if I had a
problem - unpaid plug for them
You said the problem surfaced last Summer. Did the problem go away
again
last Winter? Over the years, I've run into many situations where
outside
humidity appears to have a reasonably strong correlation to problems
within
a 'temp/humidity controlled' environment - my belief is that it is
because
some of the raw materials [solvents for example] are not stored in as
good
of a temp/humidity controlled environment.
If the problem comes and goes, I would start by pulling a roll of the
label
stock and the ribbon into a dessicant chamber to dry out, while placing
another pair into a known moist environment - and compare the results
from
both.
Is the pH of the bath changing with respect to time?
There is likely not much to be gained, but you might run an FTIR - IR
Spectra on the old and new ribbon to verify relative proportion of
constituents and confirm there were no new components [and no missing
components]. Just have them dissolve in acetone, or something, and do a
comparative scan.
The label material itself - can you do a wetting angle test on the old
and
new labels to see if there is anything significant with respect to how
well
the ink may adhere in the first place? Do you see differences with
something simple like a Scotch tape test on the printed ink, before
solvent
exposure?
I am sure that you have been over the equipment looking for thermal and
pressure differences.
Sorry I can not be of direct asssistance
Steve C
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