There are many types of varnishes used in printing and packaging, but the most common ones can be divided into three categories: oil-based varnishes, water-based varnishes, and UV varnishes. As printing trends shift towards more environmentally-friendly solutions and regulatory requirements become stricter, the use of oil-based varnishes is declining, while water-based and UV varnishes are seeing increasing adoption. Let's take a closer look at the key differences between these two types of modern varnishes.
Water-Based Varnishes
Water-based varnishes (also called water-based lacquers or dispersed varnishes) are primarily composed of water-soluble resins and water-dispersible resins. They are non-toxic, odorless, and eliminate the health and environmental hazards associated with traditional solvent-based varnishes. Water-based varnishes offer several advantages:
- Fast drying time
- Good transparency and film clarity
- Stable performance
- Versatile equipment compatibility
- Excellent abrasion resistance and smoothness
- Broad post-print processability
- Good heat-sealing properties
- Safe and convenient for storage/transport
These qualities make water-based varnishes increasingly popular for food, pharmaceutical, and tobacco packaging applications.
However, there are a few typical issues to be aware of with water-based varnishes:
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Ensuring proper drying of the underlying ink layer after applying the water-based varnish. This can be addressed by ensuring the varnish has good breathability and by moderately increasing air temperature.
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Lower gloss levels compared to UV varnishes. This can be mitigated by adding small amounts of high-boiling solvents to the water-based lacquer to improve wetting and film formation for a smoother, glossier finish.
UV varnishes are cured by exposure to ultraviolet light, allowing for very rapid curing at low temperatures without the risk of the inks underneath fading. This makes them well-suited for many paper-based printing and packaging applications like containers, labels, book covers, and cartons.
UV varnishes have several key advantages:
- Extremely fast curing with UV exposure
- Low-temperature curing prevents underlying ink fading
- Excellent adhesion to inks
- High solids content for efficient usage
- Negligible volatile organic compound emissions
- Low energy consumption during curing
- Enhanced abrasion resistance, chemical stability, and durability of the cured surface
- Easy post-processing with no sticking/blocking issues
The combination of rapid curing, strong ink adhesion, and durable, non-tacky finish makes UV varnishes a popular choice for enhancing the appearance and protection of printed materials.
In summary, both water-based and UV varnishes offer significant benefits over traditional solvent-based options, with their own unique strengths. Understanding the tradeoffs can help printers and packagers select the most suitable varnish technology for their specific applications.
