Silver -> low-chem violet; temperature compensation?

radjivand

New member
Hi all,

first of all a great forum running here, have been browsing for a few years… :)

Our company is running a small CTP for B3 Komori. The CTP unit is a Screen PlateRite Micra which images silver-halide based plates (Agfa LAP-V). OLP is from G&J. To reduce the hassle with cleaning and waste we're interested in laser upgrade from 5mW to 60mW + new processor to use low-chem violet plates. Laser upgrade is possible, but Screen stated that it will not work with Fuji plates because of lack of the "temperature compensation system". Temperature compensation cannot be added to our CTP and therefore they are not recommending this upgrade.

Now, there's the problem and please correct me if I'm miles wrong: temperature compensation should affect plate size because of the aluminium properties?

So I asked Screen about this and I get "temperature compensation system is needed because the temperature affects emulsion". I also got confirmation that there are no problems with violet plates from Agfa. I also know there are differences between Agfa and Fuji low-chem processors and they are not compatible with each other.

But what is the exact cause of this issue? How is Fuji's emulsion different from Agfa's?

It also has to mean that all CTP-s which are running Fuji plates have this "temperature compensation system" to control the emulsion. Do they?

I also assume that Agfa's violet units are mainly intended for Agfa plates. Is anyone using Fuji violet plates on an Agfa machine? What about this "temperature compensation system"?

Regards,

Arne
 

VladCanada

Well-known member
"temperature compensation system" IMHO related to Laser exposure stabulity but not to silver-halyde technology of plates emulsion and Aluminum base
 

radjivand

New member
"temperature compensation system" IMHO related to Laser exposure stabulity but not to silver-halyde technology of plates emulsion and Aluminum base

So this means that optical stability of a laser is far more important for Fuji plates but not for silver-halide and Agfa low-chem plates?

This still seems a bit weird: plate sensitivity is about the same for Brillia Pro-V and :N94-VCF or Azura V.

Can you suggest further reading about the exposure stability?
 

gordo

Well-known member
Laser upgrade is possible, but Screen stated that it will not work with Fuji plates because of lack of the "temperature compensation system". Temperature compensation cannot be added to our CTP and therefore they are not recommending this upgrade.

Now, there's the problem and please correct me if I'm miles wrong: temperature compensation should affect plate size because of the aluminium properties?

Usually the term "temperature compensation" with CtP means that the bitmap that will be exposed to the plate is scaled so that the image on plate has a constant size despite changes in ambient temperature. Aluminum plates expand and contract with temperature change as much as film - a 5° change in temperature will result in a half row of dots @ 175 lpi misregistration plate to plate.

But, because they are referring to the "emulsion" they may be using the term to refer to the focussing system. I don't know that particular Screen device, however, if it is a fixed focus device then as the thickness of the plate and coating changes with temperature changes it may exceed the range of the focussing system. Just a thought.

best, gordo
 

BillJ

Well-known member
I cant speak for the Screen unit, but the violet CTP devices I'm familiar with don't have temperature compensation. The do have cooling systems on the laser to keep the diode stable. They are also fixed focus.
 

radjivand

New member
Usually the term "temperature compensation" with CtP means that the bitmap that will be exposed to the plate is scaled so that the image on plate has a constant size despite changes in ambient temperature. Aluminum plates expand and contract with temperature change as much as film - a 5° change in temperature will result in a half row of dots @ 175 lpi misregistration plate to plate.

Well, that's what I meant at start and was wondering why hasn't this affected us already :)

I don't know that particular Screen device, however, if it is a fixed focus device then as the thickness of the plate and coating changes with temperature changes it may exceed the range of the focussing system.

It's a flatbed B3 CTP, here's a marketing pdf. IMHO (might be wrong, though) this CTP is not a fixed focus system. Also if both 5mW and 60mW options exist and the 60mW one is suitable for other violet plates, how is Fuji so different?!?

Also I could not find :Azura V or :N94-VCF sensitivity specs, mJ/cm2. As for the cooling - would it be reasonable that Screen is providing a certain 60mW laser for re-badged units which are Fuji capable but uses another one for Micra?
 

marktonk

Well-known member
As far as I know, the only violet CtP with temperature compensation is the Prosetter. Just a thought, the silver violet plates has a wide environmental range and is fairly robust. Could it be Screen was referring to the plate technology? The Fuji plate is a photopolymer plate and humidity swings can effect the plate. This is not isolated to Fuji but the photopolymer plate technology in general. It works well but has a narrower specification. so perhaps they are referring to the imaging environment and not the CtP?
 

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