Introduction:

In principle we have to differ between physical drying and chemical curing/ film building. In the following, the four main mechanism are shortly described.

1. Penetration

Drying act:

• Physical drying process
• Printing material absorbs the thinner of the ink
• Drying in seconds
• Part of drying process in printing inks and water based varnishes in cold-set the only drying process.  For example, news paper web offset.

2. Oxidative film building

Drying act:

• Chemical film building
• Parts of the printing ink react with oxygen
• Dryer compounds speed up film building
• Film building in hours
• Oxidative film building is a partial process in conventional printing inks.

3. Evaporating

Drying act:

• The water particles of the varnish are transformed in a steam like condition
• The steam, or respectively, the steam saturated air will be exhausted
• Drying in seconds or up to minutes

Hint:
The evaporating drying is a partial process of the drying of varnishes. The drying process of water based varnished will be explained in the following.

4. Polymerization UV curing

Curing act:

• UV radiation and photo initiators are starting the series of polymerization processes
• Curing process in milliseconds