Digital BW, The Print

By the way, in one centrifuge test I stuck in a sample of 7800 LLK.  As you'd expect, it's quite stable in terms of the Lab L.  What surprised me is that the Lab A changed.  The top of the test tube changed from Lab A = 0.05 to Lab A = 0.2.  This is way more than I've ever seen any carbon ink change.  

The K3 LLK is too green to me, and I've suspected that Epson put in a bit of cyan.  This centrifuge test is consistent with it being a blended ink.

Paul
www.PaulRoark.com

On Oct 5, 2009, at 12:12 AM, pr_roark wrote:

> By the way, in one centrifuge test I stuck in a sample of 7800 LLK.   
> As you'd expect, it's quite stable in terms of the Lab L.  What  
> surprised me is that the Lab A changed.  The top of the test tube  
> changed from Lab A = 0.05 to Lab A = 0.2.  This is way more than  
> I've ever seen any carbon ink change.
>
> The K3 LLK is too green to me, and I've suspected that Epson put in  
> a bit of cyan.  This centrifuge test is consistent with it being a  
> blended ink.

Have you given the HP grays a whirl?

C. David Tobie
Global Product Technology Manager
Digital Imaging & Home Theater
CDTobie@...


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Datacolor
www.datacolor.com/Spyder3


[Non-text portions of this message have been removed]

C D Tobie <CDTobie@...> wrote:

> Have you given the HP grays a whirl?

Yes, they are blended carbon and color.  I don't know that I have good enough data to compare the 2 in terms of separation, however.  

With the HP inks the blending became very obvious the first time I worked with them.  The magenta stains the equipment just like it does with the MIS blended inks.  I have not noticed that with the K3 LLK.

Paul
www.PaulRoark.com

Paul:
Centifuging will not necessarily give you the results I think you want. This typically separates heavier particles from lighter ones. As you know, all pigmented inks are "ground" to try and get a more uniform particle size. In the end, there is still some clumping. The centifuged results should just give you different color balances depending on the kind of clumping that has taken place. It would be interesting to see if when carbon grays are mixed with color pigments, if they "clump" individually, or with each other. I would venture to guess it would depend on ionic forces.

When my old ink partner Takichi Maertz was experimenting with B&W printing with dilutions of dyes, we did some work with paper chromatography to determine the composition of both pigment and dye inks. You might try that in addition to your centifuging experiments.

The settling situation is again another animal. While today's pigmented inks are sooooo much better when it comes to settling, you will still have it occur to some extent when inks are allowed to sit undisturbed. The carrier/co-solvent of course is of paramount importance here.

Paul, I applaud you continuing research and sharing on with the community, your results. Keep up the good work!

John Nollendorfs

   

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "pr_roark" <paul.roark@...> wrote:

>
> C D Tobie <CDTobie@> wrote:
> 
> > Have you given the HP grays a whirl?
> 
> Yes, they are blended carbon and color.  I don't know that I have good enough data to compare the 2 in terms of separation, however.  
> 
> With the HP inks the blending became very obvious the first time I worked with them.  The magenta stains the equipment just like it does with the MIS blended inks.  I have not noticed that with the K3 LLK.
> 
> Paul
> www.PaulRoark.com
>

"John" <jrnolly@...> wrote:
>
> Centifuging will not necessarily give you the results I think you want.

I wasn't really looking for color (lab a & b) changes.  My only concern with the carbon pigments is Lab L from settling.  I just stumbled into the Epson LLK Lab A variance. 

With respect to the Lab L, centrifuging the inks correlates quite well with the density changes I've observed in actual printing and working with printers.


>... we did some work with paper chromatography ...

Yes, that is how I first detected the color in our old B&W inksets.

 
> ... when it comes to settling, you will still have it occur 
> to some extent when inks are allowed to sit undisturbed.

Yes, but the rates can differ significantly.  That's what I'm looking at in making decisions that trade that off against other things, such as how well the ink will penetrate watercolor paper surfaces.  By knowing the settlement rates I've been able to design around dilute carbon's inherent issues with excessive warmth.    

Part of what I envision is a modification of the 7800 that would allow these lighter viscosities and smoother Arches printing -- if needed.  

> The carrier/co-solvent of course is of paramount importance here.

You've seen me trading off glycol for glycerin, as well as adding a new surfactant to the mix.  Glycerin's high specific gravity seems to really help with the suspension, and it's very user friendly.

The surfactants are very interesting...

Paul
www.PaulRoark.com