Digital BW, The Print

On Friday, August 8, 2003, at 12:06  PM, joe davajon wrote:

> In response to Robert Morrison:
>
> Robert,
>
> I’m glad you take such a great interest in this forum.  I’ve read all 
> of
> your posts with great interest and have found most of your remarks
> interesting and informative.  But, I must amicably disagree with 
> several of
> your assertions when you responded to my Hydrocote Spraying.
>
> First:  You state that one spraying should use a respirator.  This 
> material
> is non-toxic.  But to be sure, I called the manufacturer  who assured 
> me
> that a respirator was not necessary when spraying.

My first bachelors degree was in Chemistry and I worked as a polymer 
chemist for 5 years before getting another degree in art.  The 
co-solvent in Hydrocote is N-methylpyrolidone (NMP) which has by some 
testing been shown to be a carcinogen.  It is used in Hydrocote in 
concentrations of 5-10%. It is necessary to solubilize the hydrocote 
polymer and monomers...which are not soluble in straight water.  NMP is 
more volatile than water and will be in much higher concentrations when 
you spray it.  If you read the MSDS you will see all of this.  Wear a 
respirator if you spray anything except water...period.

> You asked me if I have
> ever  heard of overspray.  Yes, Robert,  I’ve heard of overspray.  But 
> while
> you seem to suggest that there is a lot of waste because of overspray, 
>  I
> can assure you that isn’t true.  When I used my HVLP gun I got a ton of
> overspray which practically filled my garage.  I abandoned that 
> approach
> immediately.  It must be remembered  that I am using a touch-up gun 
> which is
> small.  It produces very little overspray but being a cautious person 
> I do
> leave one of the garage doors open just to be doubly safe.

HVLP sprayers were specifically developed for low overspray compared to 
LVHP sprayers...which is what you are using...that's a simple fact.  If 
you were getting more overspray from your HVLP sprayer then you 
apparently weren't using it properly.
>
> Second:  Your concern about curing is obviously important.  I can 
> assure you
> that my sprayed prints feel as dry and hard as my Mayer Rod applied 
> ones.  I
> can’t tell the difference between them. You stated categorically that I
> would  “…never get a full cure…” with my method.  May I respectfully 
> ask how
> you can be so positive?

Because aliphatic polyurethanes take up to a week to cure and need to 
be exposed to air to do that.  The instructions on the Hydrocote can 
specifically say, that while the polymer may feel dry in an hour, you 
should wait 2 hours prior to recoating.  This is the reason.  When 
using water based polyurethanes the conventional wisdom is to wait a 
full day. The benefit of the Mayer Rod is that you only need one coat 
when you are using a #30 rod.  You can then put the print in a drying 
rack and allow it to fully cure.  Doing this in multiple coats without 
adequate drying/curing is asking for trouble, because residual monomer 
can become trapped in the film layer.  This could result in premature 
yellowing and breakdown of the print.
>
> Finally, I know you’re working on a method to coat larger than 13x19 
> inch
> prints.  If I recall accurately,  that method will entail some 
> significant
> expense and require specialized equipment.  Do you have any details to 
> share
> with the forum?  On this subject,  I feel very confident that I can 
> use my
> Badger Touch-Up gun to spray any size print.  Size doesn’t matter. 
> It’s like
> painting a car: you spray each section a bit at a time until you’ve 
> finished
> the entire car. Size is irrelevant.

Good solutions for rod coating larger prints (bigger than 16x20) don't 
exist now, but one company is working on designing a piece of equipment 
to do this.  Sorry I can't say any more than that at this point.
>
> Once more, the bottom line for me is that if it works use it!  Mayer 
> rods
> simply don’t work for me.  Spraying does.

Great.  I'm just trying to share my expertise in coating technology and 
relate what I believe will be the most successful approach to coating 
for the majority of users.  I'm glad to hear that you are spraying in 
your garage, and not your house or studio...that's good.  Aside from 
that I would strongly suggest wearing a respirator for any type of 
spraying...even airbrushing...don't take chances with your lungs.
>
> P.S.  I wonder if it’s possible to see some of your photography?  I’d 
> like
> to see your work.
>
Web site is in progress...hopefully to be released in the next month or 
so...but you won't really be able to see the benefits of coating from 
this.  Sounds like you already have seen the benefits, however.

Happy coating,

Robert