Measuring Opaque White TVI on Metallic Substrate

[chevalier]

I have come across a project that uses a lot of opaque white ink screens as an effect on a metallic substrate. I realize that once we get on press we're going to almost certainly need to perform some dot gain calculations and generate curved opaque white plates.

I'm thinking that if I invert my measurement differences that I'll be able to achieve this. I would like to note that I do realize that the screens themselves aren't actually inverted. A 20% screen of white is effectively the same as a 80% print of metallic in theory (the screening being inverted in this measurement case). Upon measuring a control mark and seeing 85% then I would be printing 5 points sharp (dot loss) and that if I see a 75% I'm gaining 5 points (dot gain).

I'm lucky enough to have a calibrated Xrite Platescope XRD60 (https://www.xrite.com/platescope) that has been verified to a proof on substate (Fujifilm Finalproof) to at least give readings on the substate at least exhibit what I'm theorizing above. I tested with all the available spectrums: Red, Green, Blue, RGB ("White"), UV and Infrared and Red seems to provide the most sound and consistent results. I also have an i1Pro2 and eXact but I've found the quick down and dirty dot gain calculations for spot colors are generally easier with the XRD60.

Am I on the right track or have I lost my mind?

 

[David Milisock]

Your method seems 'solid' enough and in theory, it should work. Good luck setting a curve for it however as my experience with Opaque White is that you have to put a lot of it on there to get it to cover anything correctly.

I think printing with Opaque White is more of a Craft than a Science and I'm not sure how an instrument can tell you when enough is enough. Especially when the idea to begin with is for little to no substrate show-through.

​Agreed, we use whiteners depending on the base materials color.

 

[chevalier]

For solids we generally use two units to print white "two hits"; the second hit with extra pull back. Getting a measurable solid isn't really challenging. You can use straight density or LAB for that as long as you have a patch of each hit of white and then a 200% trap of both. I've even been able to get the press' in-line spectro to handle this in real time.

My concerns are the screens and whether they'll be accurately read by a measurement because they'll be a single hit and not truly opaque. I'm thinking that a spectrodensitometer will not work but that the platescope will due to the different ways they are calculating TVI (or at least how I understand it). Either way I'll give report on the outcomes and what did and didn't work for the collective community knowledge.

 

[Alois Senefelder]

Why not think it as a ............... Mono H/tone Black Printer Separation,

Stupid answer or what ??


Regards, Alois

 

[D Ink Man]

Do you have room for solid color bar patch('s) ?

 

[Tim-Ellis]

My concerns are the screens and whether they'll be accurately read by a measurement because they'll be a single hit and not truly opaque. I'm thinking that a spectrodensitometer will not work but that the platescope will due to the different ways they are calculating TVI (or at least how I understand it). Either way I'll give report on the outcomes and what did and didn't work for the collective community knowledge.[/QUOTE]

When we double hit on our indigo press we have two different routes. One where only solids are hit double and another where screens and solids are hit double. Do you have a similar option available to you?

 

[D Ink Man]

Another, and perhaps the best way to control the amount of opaque white that is being laid down is the use of an Ink Fiilm Thickness Gauge. Measuring the thickness on the vibrator roller of the ink film will give you constant density on your printed subject. Your tolereance should be +/- .05 mil to produce exacting density of the ink, sheet to sheet, job to job.

D

 

[aqazi81]

Another, and perhaps the best way to control the amount of opaque white that is being laid down is the use of an Ink Fiilm Thickness Gauge. Measuring the thickness on the vibrator roller of the ink film will give you constant density on your printed subject. Your tolereance should be +/- .05 mil to produce exacting density of the ink, sheet to sheet, job to job.

D

Is it really possible with just an Ink Film Thickness Gauge?

 

[D Ink Man]

Is it really possible with just an Ink Film Thickness Gauge?

Yes, it is absolutely possible and completely foolproof, repeatable and reliable.

D

 

[aqazi81]

What do you think?

May be Erick has an answer for this.

 

[aqazi81]

Yes, it is absolutely possible and completely foolproof, repeatable and reliable.

D

Can you explain it how?

 

[D Ink Man]

Erik will probably have an answer for this but I doubt if he has ever actually used one.

D

 

[aqazi81]

I'm referring to practicality. If you've ever used one and understand their intended design, the answer is obvious.

I haven't used that gauge.

 

[D Ink Man]

No, the vibrator roller (steel) and keep the tolerance at +/- .05 mil. Repeated again here for emphasis. :;

Then you can take the densitometer for other means and use it for tasks it was designed to do.

D

 

[aqazi81]

No, the vibrator roller (steel) and keep the tolerance at +/- .05 mil. Repeated again here for emphasis. :;

Then you can take the densitometer for other means and use it for tasks it was designed to do.

D

As far as I know the densitometer is also measuring the same thing on sheet. One way is mechanical and the other way is optical.

 

[chevalier]

OK - so my idea was successful with the platescope but did not work with an i1pro2 or eXact. I was able to generate a relatively nasty curve straight to the real numbers but matched it to an Esko pressync curve that smoothed it out very well and produced pretty spectacular results. For the record, even a pure UV opaque white does not like to screen - at all - but running this at 300lpi made the nastiness visible only to someone viewing under magnification.

Below is a copy/paste of my spreadsheet that I used to do the down and dirty curve calculations. The validation sheet was within <>2 points at each measurement.

Target (Plated)	Measured on Platescope under Red light spectrum (Printed Sheet)	100	Difference	-1	"Actual" Read
5	97	3	2	-2	3
10	89	11	-1	1	11
20	75	25	-5	5	25
30	64	36	-6	6	36
40	54	46	-6	6	46
50	43	57	-7	7	57
60	33	67	-7	7	67
70	20	80	-10	10	80
80	15	85	-5	5	85
90	11	89	1	-1	89
95	9	91	4	-4	91
		100 less Measured Value		Invert the difference	Esko Press Sync Curve E43

 

[D Ink Man]

OK - so my idea was successful with the platescope but did not work with an i1pro2 or eXact. I was able to generate a relatively nasty curve straight to the real numbers but matched it to an Esko pressync curve that smoothed it out very well and produced pretty spectacular results. For the record, even a pure UV opaque white does not like to screen - at all - but running this at 300lpi made the nastiness visible only to someone viewing under magnification.

Below is a copy/paste of my spreadsheet that I used to do the down and dirty curve calculations. The validation sheet was within <>2 points at each measurement.

Target (Plated)	Measured on Platescope under Red light spectrum (Printed Sheet)	100	Difference	-1	"Actual" Read
5	97	3	2	-2	3
10	89	11	-1	1	11
20	75	25	-5	5	25
30	64	36	-6	6	36
40	54	46	-6	6	46
50	43	57	-7	7	57
60	33	67	-7	7	67
70	20	80	-10	10	80
80	15	85	-5	5	85
90	11	89	1	-1	89
95	9	91	4	-4	91
		100 less Measured Value		Invert the difference	Esko Press Sync Curve E43

Respectfully,

Is this not killing a fly with a sledge hammer?

D

 

[chevalier]

Respectfully,

Is this not killing a fly with a sledge hammer?

D

I can certainly see how you would get that impression. It took about 45 minutes, 2 litho plates and about 100 press sheets. Considering the size of the job (~50,000 full size sheets) and it being on a very expensive metallic substate it was well worth the cost, time and energy to make it print correctly. Customer attended the press approval and personally signed off.