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Ink And Film Density

The purpose of a printed film positive is to block UV light during screen exposure. Films may or may not look dark, the UV light blocking ability is the key to success.

How can you tell if your films have the right density (Dmax)?
Most users will NOT have the proper transmissive Densitometer to read the actual percentage of light that is being blocked by their films and relying on your “eyes” is not the best way since humans can not see UV light.

First, understand that “density” is not the “only thing” that matters, it’s the amount of Ultra Violet (UV) light blocked that really matters. Just as with the older product called Rubylith that we cut with x-acto knives to make films, you can see through it, but it blocks 100% UV light making it perfect for screen making. It’s the same for sunglasses.

Density vs UV blocking:
Light can be blocked through density alone since light can not pass through a solid object, but films are not always 100% solid.
Using Freehand® Dmax® black dye ink with UV inhibitors mixed in will block greater than 99% UV light.

Human eye test for those that do not have a Densitometer:
Dye ink – if you hold your film up to a bright light or a bright window you should see slightly through the 100% print areas so that images look very dark and lacking detail and the overall appearance should have a red tint about it. That is probably close to a 4.0 dmax with light UV blocking and that is good.

Pigment ink – is obviously different, it’s not water based like dye ink. Its archival ink for sign making. Pigment ink  has a chemical base with radical particles that form a light blocking bond. It is very easy to see through pigment ink. Best to use Dmax dye. You can use pigment but it will require tweaks to your screen exposing supplies and standards. Dmax will always burn cleaner and wash out faster, capturing more detail easily. 

Use AccuRIP’s Droplet Weight Density TEST Print feature under AccuRIP’s File Menu (not available in SE). It will produce 15 droplet weights per resolution. Print the test to film. Let it dry, then expose a screen. Wash it out and review the result,

Cost? Pigment inks and film cost more which is why so many users choose dye.

Availability: Dye is easier to get through industry suppliers.

Important Tip:
The use of waterproof film is critical to your success. Nott hat non-waterproof will not perform in some cases – it is not recommended. The emulsion layer on the film grabs the ink.



(c) Freehand Library Article / AccuRIP / Separation Studio NXT / Spot Process / Dmax / Amaze-Ink / DarkStar

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