Digital BW, The Print

----- Original Message -----
From: "Robert Morrison" <rmorrison@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Monday, September 23, 2002 7:13 PM
Subject: Re: [Digital BW] Coating, was Photogravure


> On 9/23/02 1:31 AM, "Ernst Dinkla" <E.Dinkla@...> wrote:
>
> > There's a general attitude in the printing industry that varnishes may
be
> > worse than the inks themselves.
> > In the past the risk of varnishes getting yellow or brittle on hardening
and
> > UV exposure was something to count with. I'm using some of the best
outdoor
> > vinyl inks in silkscreen printing: Sericol's Polyplast E series.
> > In the specs pages they advise to use them without an overprint varnish.
> > Only where the surface may be subject to abrasion etc they advise to use
a
> > Polyplast varnish.
>
> It is impossible to make general statements about varnishes yellowing.
> There is a very large range of possible polymer technologies.  Some of
them
> yellow badly (e.g., polyurethanes) while others are quite good.  The
> manufacturers of products frequently make decisions based on their
potential
> use which frequently require shot term display and the product needs to be
> cheap.

I have to agree on that but the problems we have had in the past were not
the result of  of cheap materials but rather bad advice from ink suppliers.

We print quite a lot of different varnishes. UV curing varnish on offset
printed material, spot and full size is most of that work. The problems over
a 25 year experience have been with two component epoxy varnish and an
alkyde varnish for outdoor work, yellow casts or too much hardening as a
result. Both printed on difficult substrates like Alucobond with a white
polyester coating or Melamine. Acryl couldn't be used. Normaly Acryls were
best in my experience, there are varieties of acryls and copolymeres of
course and it is hard to tell what is in it and what makes the difference.
Manufacturers are not that open. Of the varnishes that we have none is
usable for inkjet paper so far. Not to my taste I should write.

ERnst