[BnC Custom Ink]

What are the pros and cons?

Will one work for some jobs and the other work for others?

Where does diazo fit in, is all dual cure diazo sensitized?

Is there any other type?

Please discuss.....

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[sben763]

I use all photopolymer. Pros long shelf life. Cons less window for proper exposure. Little under it will blow out easily a little over and usally not salvageable

Dual cure diazo is all sensitized. Pros longer window for exposure. You can miss by under or over exposure and still get good results. Cons short shelf life but with proper storage and handling can be used longer than manufacture suggest.

Dual cure can be better for most when doing halftones due to the larger window. I did 1 halftone job years ago with dual cure and first time was no problem. Didn't do a anything but spot colors next 2 years and had switched to photopolymer, at first I suffered a bit with halftones and switched emulsions to several different photopolymer. Found a great photopolmer and my proper exposure time and no problems. Never relized Why till it was discussed here on TSF and if I remember right it was ScreenFoo who brought it up.

 

[ScreenFoo]

Hmmm... I can start it off here, but this is a subject worthy of a lot more discussion than I can offer.

I'll preface by saying "as I understand it."
I'm hoping people can find good resources to correct me wherever I may be wrong. (I enjoy learning )

Diazo sensitized emulsions have been around for quite a while. They take a good amount of time to expose, and have good to excellent reproduction capability. They are also relatively inexpensive. Their UV 'reactive' wavelengths on most I've seen charts for spike around 370 and 420 nM or so. They can have excellent solvent resistance, or excellent water resistance--but not both--not the best choice for the plastisol printer in a very humid climate.

Photopolymer (of which SBQ is a popular variety of) is a type of pre-sensitized emulsion that offers a similar level of reproduction as diazo, but only under much more controlled circumstances--it's exposure latitude is extremely short. I'm interested in learning more about the UV reactivity on these--not sure if it's common to all types to have a broad spectrum from 350-450 or so they're reactive to. They are usually more expensive than Diazo emulsions, but are similar in their solvent resistance problems ("solvents" as well as the universal solvent--water). They seem to be a good choice for weak light sources for exposure, as well.

Dual cure is a mix of the two. I can only surmise that the combination of one water resistant component, and one solvent resistant component is why these are superior. (Haven't seen any good articles that explain the reasons why they work so well) It seems as if you get the best of both worlds--reasonable exposure time but a higher water *and* solvent resistance than either component on it's own. They have the best reproduction capability, exposure latitude, mesh bridging, and mechanical and solvent resistance of the group.

I haven't used any dual cures that are not diazo sensitized--this is not to say there aren't any.

Edit: Ha--took too long writing that--Sben, I am indeed a fan of the dual cures. I've made many thousands of stencils with LX-680 or Poly plus S and only a thousand or two with anything else. Not to say I don't like playing around, but they're consistent, and forgiving, like I try to be.