Digital BW, The Print

Paul, you wrote:

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>>With an extra printer for glop/varnishing it would be possible to use a 
>>two component resin, one component per head. ...
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>The 2 component polyurethanes can be very strong coatings.  I wonder in the
>inkjet setting if the 2 jets of it would overlap properly for mixing.  Even
>if they overlap sufficiently, is there enough mixing on the paper to avoid
>having the separate components only partially mixed and cured?  I'd also
>want to be sure there was no setting up of the PUR on the head or parking
>pad.  I'm not sure if the UV cure types stay totally liquid in the absence
>of strong UV or if they would slowly cure on the head and parking pad.
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>With those caveats, however, I think the 2 component approach has great
>promise for coatings and inks themselves.
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The UV curable aliphatic polyurethane that I have here is too thick for inkjets and probably too aggressive for the rubber/elastomere components of the capping station, wiper, seals of the Epson. It also isn't a nice varnish for matte papers as it penetrates the paper too much and by that isn't easily cured with UV light, it keeps its smell when not cured so I think you better forget that. On gloss it is nice but you need a UV curing unit. It will not cure without enough UV light so that's not the problem.

Two components on an Epson 9000 is also a risk as the wiper blade runs from black to yellow and will bring one component in contact with the other component on the heads themselves. Running without a wiper blade is the only option and may not be as stupid as it looks, applying a varnish with more heads doesn't rely on all nozzles functioning. The 10000 has another wiper system.  The three  wiper blades run over the 3 head assemblage of that printer from top to bottom so there the risk of mixing on the head is lower. I'm not afraid of the varnish not mixing on the surface of the paper, it will be an acceptable layer thickness and migration of the agents within the layer happens. 

I'm more interested in the Staedtler ink base however. The inks are already tested on Epsons. But nowhere is a description what the gloss of the ink is. There's a silkscreen printshop supplier nearby that sells the ink, will get some samples of prints and ask Staedtler for bulk base. They claim a good fade resistance for the inks. Comparing them with silkscreen inks and Vutek outdoor inks. The gamut should be better than Mimaki's pigment inks but the last are not at Epson's level. Printing on uncoated aquarel paper is mentioned. Heating isn't required on porous materials but I guess not forbidden either, a resin in the ink melts according to the webpage. All in German however. No Staedtler on the PMA ?

Ernst