Lacquer vs Varnish vs Shellac vs Polyurethane vs Conversion Varnish

Lacquer, Varnish, Shellac, Conversion Varnish, and Polyurethane all serve to protect a wood product from water, heat, and other spills.  By applying a topcoat you can have a finished wood project that lasts for a long time to come. However, each type of finish has a variety of pros and cons that you should consider to better determine which may be right for your application. We will cover the pros and cons of Lacquer, Varnish, Shellac, Conversion Varnish and Polyurethane in this article so you can better determine which is right for your application.

Lacquer

Lacquer was introduced in the 1920’s and touted to be the ultimate wood finish.  It offered ease of application and better resistance to water, heat, alcohol, and acids.  Additionally, it was synthetic which made it more available than the common alternative at the time, Shellac. Lacquer is available in two types for wood – nitrocellulose and butyrate or (CAB). Cab is typically a bit more expensive but has less yellow of a tint which allows it to remain clearer as it wears over time in comparison to nitrocellulose lacquers.

Pros of lacquer

• Fast drying which makes it ideal to be applied with a spray gun like a Binks Trophy Spray Gun or an Air Assist Airless (making it one potential option for production finishing work)
• Tolerates climate differences well – Lacquer is compatible with a variety of solvents which you can choose an appropriate solvent to help compensate for any weather conditions
• Ease of repair – Since lacquer cures through evaporation quickly it can be easily repaired or removed compared to other finishes
• Quick drying time can help reduce issues with dust settling in your finish
• Relatively Low Cost
• Variety of appearance – Due to a lot of formulations that are available it is available with a variety of appearances

Cons of Lacquer

• Has high VOC content which is harmful to the environment
• Less resistant to heat, solvent, acid, and alkali when compared to varnish
• Limited scratch resistance
• Low solid content results in poor film building properties

Varnish

Varnish which includes polyurethane and conversion varnish is the most durable of the finishes.  It protects well against heat, solvents, acids, wear, alkyds, and water.

Pros of Varnish

• Resistance to heat, wear, solvents, acids, and alkalis – the crosslinking of resin molecules result in an extremely durable finish. It takes significant exposure to solvents, acids, alkalis, or heat to damage a varnish finish
• Resistance to water – again due to the crosslinks that are formed varnish excels at preventing water from passing through
• Easy to brush and hard to spray (with the exception of conversion varnish)

Cons of Varnish

• Slow Cure times – Varnish takes a long time to dry which is why it is easy to brush on as you have a lot of time to work with. However, the long dry time allows for greater potential for dust to settle in your finish
• Not sprayed easily (except conversion varnish) – due to overspray floating and long cure times varnish can present problems in getting a clean finish when spraying (unless using conversion varnish)

Shellac

Shellac is one of the original protective wood finishes and has a variety of benefits and drawbacks.

Pros of shellac

• Provides an excellent barrier for water vapor, silicone contamination, and existing stains which means it is sometimes used as a sealer coat
• Is one of the best touchup finishes for repairing dings and scratches in any wood finish
• Uses mild solvents making it less harmful to the environment

Cons of Shellac

• Weak protection against heat, water, solvents, and chemicals – this makes it less than ideal for tabletops or high use furniture pieces
• Weak resistance to wear
• Short shelf life

Conversion Varnish

Conversion varnish is a varnish that has a catalyst that is added to accelerate dry time, this is the most common type of varnish that is applied with a spray gun .

Conversion Varnish Pros

• Extremely durable finish with same protective properties of varnish
• Is good for spray finishing as it dries quicker due to catalyst being mixed in the coating
• Very attractive clear finish coat
• High solid contents requires less coats to build an appropriate film build

Conversion Varnish Cons

• Have to dispose of left over coating as catalyzed material cannot be stored
• Require skill in application – if too thick of a film build is applied the finish can often crack
• Requires good climate control – typically post catalyst varnish must be applied in a minimum of 60 degrees for proper results

Polyurethane

Polyurethane is actually a form of varnish and is very durable. They come in two parts or cure with heat or by absorbing moisture

Pros of Polyurethanes

• One of the most durable coatings – Polyurethanes within the varnish category are one of the most resistant to scratching , heat, alkyd, acids, and wear
• Beautiful appearance – Polyurethanes create one of the most attractive protective finishes after application

Cons of Polyurethanes

• Long dry time – a typical polyurethane can take up to 24 hours to dry
• In between coats requires sanding – typically polyurethanes will require sanding between coats as it will not bond without proper preparation between coats
• Usually is brushed on making it slower to apply but you can learn about spraying polyurethane here

Final thoughts

Ultimately if your looking for the easiest spray application with good durability you can consider lacquer, if you want a good spray finish with even better durability you may consider a post catalyzed lacquer. For durability and easy brush on application varnish can be a great solution. Touch up work is often well suited for shellac. Ultimately selecting the right finish will depend on the qualities that are important for your application and by reviewing the pros and cons of each you can decide which is right for you.