INFRA-RED

Both infra-red and ultraviolet curing processes are enjoying increasing popularity, with sales increasing year by year. However. although the processes are often thought of as interchangeable methods of drying print, there is actually a world

of difference in cost, complexity,applications and the working practices required.

To fit an ultraviolet system to atypical four-colour sheet-fed press would cost around US$50, 000 and take from five to ten days.To run the system,in terms of power consumption. would cost about US$3.00 an hour The process also requires alonger learning curve than for infra-red. but for certain types of it offers advantages of quality and speed which can easily outweigh the cost and complexity of installation.

Fitting an infra-red system on the same press would cost between US$10,000 and US$25,000 and take about one day. with power consumption costing from US$2.00 to US$2.50 per hour. However. probably the most significant point about this process is that it does not require any changes in working practices or press consumables.

Compared to a press which has no accelerated facilities, an infra-red system should reduce the time of print three to four times, which is a particularly useful saving when printing work-and-tum. It also enhances gloss levels and can reduce the spray powder by up to 70 per cent; rub resistance isimproved by some 10 per cent.

HOW IT WORKS

However. to achieve all this, you need to follow a few basic rules; understanding the process will help you do this. Infra-red driers work by heating the ink film through the application of infra-red radiation. Heat is acatalyst to any chemical reaction - in this instance, the oxidation/polymerisation of a conventional offset paste ink and infra-red light is a heat source.