UV varnishes are top of the range varnishes. They have the best performance in terms of gloss and chemical resistance.
Formulation:
UV varnishes are formulated using the same chemical principles as UV inks, in other words they contain reactive resins that polymerise and form a hard film under the effects of UV radiation. The compatibility of UV inks with UV varnishes is therefore optimal.
Use:
UV varnishes can be applied by using of the ink duct, a varnishing machine or a varnishing unit ( > See “Fastnesses of inks") and require specific UV drying equipment.
They may be used in-line on UV or Flexo inks and off-line on conventional offset / letterpress inks after drying ( > See Pulsar Technical Data Sheets)
As with acrylic varnishing, it is recommended to use light fast inks because certain pigments may be chemically altered.
Formulation:
UV varnishes are formulated using the same chemical principles as UV inks, in other words they contain reactive resins that polymerise and form a hard film under the effects of UV radiation. The compatibility of UV inks with UV varnishes is therefore optimal.
Use:
UV varnishes can be applied by using of the ink duct, a varnishing machine or a varnishing unit ( > See “Fastnesses of inks") and require specific UV drying equipment.
They may be used in-line on UV or Flexo inks and off-line on conventional offset / letterpress inks after drying ( > See Pulsar Technical Data Sheets)
As with acrylic varnishing, it is recommended to use light fast inks because certain pigments may be chemically altered.
Characteristics:
UV varnishes have the best performance in terms of resistance, gloss and instantaneous drying under the effects of UV radiation.
UV varnishes have the best performance in terms of resistance, gloss and instantaneous drying under the effects of UV radiation.
Incidents
Probable causes and remeies
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Cause
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Too much anti set-off powder (if wet-on-dry varnishing).
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Remedie
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Reduce the amount of anti set-off powder. Check the particle size.
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Cause
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UV varnishing on conventional inks.
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Remedie
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Allow to dry for 24 to 48h before UV varnishing.
IR and hot air drying of conventional inks is not recommended if UV varnishing . |
2. Discoloration of the ink film (back to incidents)
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Cause
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Chemical attack by the constituents of the UV varnish.
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Remedie
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Use light fast inks: Rhodamine, Purple, Violet, Blue 072 and Reflex Blue. > See " Fastness of inks".
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Cause
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Glue/ varnish incompatible.
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Remedie
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Use a suitable gluable varnish (NdT: “dorable” in the original, but why gilding/stamping if glueing problem) or make reserves.
Use an acrylic varnish. |
4. Poor drying (back to incidents)
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Remedie
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Add photoinitiator (3% max.).
Check the condition of the lamps and reflectors. |
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