Digital BW, The Print

Clear automotive lacquers were used by photographers all the way back into the 50s, at least, for coating C-prints. The matting agent was usually a flour like silica added to it to get a suitable matt finish.

When properly done, it did help protect prints but it was absolutely needed if prints were to be framed directly against glass.
However, I saw, and made restorations of, many examples where it was not a good job and prints faded unevenly where the coating was inadequate.
Of course in those days they all faded badly over time anyway, even if more slowly and evenly when coating was well done.That problem had disastrous consequences for many small studios at the time.

Regards,
Duane

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Glenn" <glennrbarry@...> wrote:
>
> I'm not a chemist, but I do know an industrial chemist and can converse easily with him about chemistry.
> 
> Here's a curious one for you all, I received some left over concrete sealer, which is 70% Xylene solvent acrylic lacquer.
> 
> The high quantity of solvent is to aid penetration into the pores of the concrete to seal it, rather than just a top coat that can wear exposing the pores.
> 
> Breathing apparatus and skin protection is essential with it's use.
> 
> Xylene used to be the solvent in some permanent markers, some now specify Xylene free.
> 
> It's by far the best timber lacquer I have used, but is difficult to attain a perfect finish spraying or brushing.
> It dries to a full gloss finish on timber.
> It also lists UV protection as one of it's qualities.
> I haven't done a test to check for yellowing over time.
> 
> That gives some background
> 
> I tried spraying it onto a print to see if the Xylene solvent would disturb or react with the ink, in this case dye.
> No issues whatsoever.
> 
> I went so far as to saturate one section of the print, which was on Arches cold press 300GSM, till the lacquer was visible through the back of the paper.
> Again no issues.
> 
> At the time I didn't have a spectrometer to measure if there was any discernable density change, but I may be able to do some tests on a greyscale separation early next year.
> 
> Now the good part, it's $70Aud for 20 litres. That's a lot to use, actually too much, but if you do the garden path or driveway, keep some spare to try.
> However I'd also suggest auto lacquer, which is used for scratch and UV protection over metallic and pearl finishes, would be an excellent choice for some tests.
> 
> A slight variation on clear auto lacquer has been used in the surfboard industry for decades. It's a clear final coat with a matte finish, which is just auto finish with a gloss inhibitor = matte finish.
> 
> Clear Auto finishes are usually available in pressure packs for those without spray equipment. Also some auto paint suppliers can load individual pressure packs for anyone after a gloss inhibited, matte finish.
> 
> If you really want to know the chemical composition of what you're currently using - locate the MSDS (material data safety sheet). Sometimes individual elements are just listed by CAS# in an attempt at concealment. Just research the listed CAS# instead.
> 
> peace out
>