Urea-formaldehyde varnish in history
Urea-formaldehyde varnish, also known as urea-formaldehyde varnish, was a type of varnish widely used in the past, especially in the first half of the 20th century. It was mainly used in the furniture and woodworking industry to provide a tough and durable finish to wooden surfaces.
Due to these characteristics, it became popular in the guitar manufacturing sector thanks to the introduction and research of José Ramírez III. In search of an alternative to shellac (which produces very small crystallisations due to its fast drying time because it is based on alcohol) and to the greasy varnish used on violins (which produces large crystallisations that allow the transmission of vibrations not only longitudinally but also transversally, increasing the sonority), he found the urea-formol varnish which had the ideal characteristics: relatively long drying time but short enough so that the guitar could be played in a few months and, better still, it continued its crystallisation process until it was fully matured.
The discovery and application in guitars
It was thanks to an umbrella salesman who passed by the Ramírez Guitars shop that José Ramírez III noticed the varnish on the neck. Through this he was able to contact an important paint and varnish manufacturer who put his laboratory and his technicians at his disposal, achieving the most suitable formula. This varnish had a drying period that allowed it to be polished in about 2.5 to 3 months. Although its application was complex and required sanding by hand between coats, it was worth it for its rich contribution to the sound. Its total crystallisation period was 8 to 12 months, and its consistency is indefinite over time if the guitar is properly cared for.
Over time it tends to crack, but this problem has not been observed on his guitars so far, for whatever reason. Also, over time, this varnish continues to mature and benefit the sound of the instrument.
Advantages of urea-formol varnish
Hardness and resistance: It provided a hard and resistant layer that effectively protected the wood against wear, scratches and other damage.
Fast drying: This varnish tended to have relatively short drying times, allowing varnishing projects to be completed in a reasonable amount of time.
Clear finish: It provided a glossy finish that enhanced the natural beauty of the wood, allowing its grain and textures to be visible.
Drawbacks of urea-formol varnish
Toxicity: One of the main drawbacks of urea-formol varnish was its formaldehyde content, a volatile and potentially toxic chemical compound. Prolonged exposure to formaldehyde fumes could cause eye, nose and throat irritation, as well as respiratory problems and allergies in some people.
Yellowing: Over time, urea-formaldehyde varnish tended to yellow, especially when exposed to direct sunlight, which adversely affected the appearance of the finish. However, in the case of Ramirez Guitars, this is not noticeable due to the characteristic reddish colour used in the varnish.
Cracking: In some circumstances, the urea-formol varnish could experience cracking or crazing over time, especially under conditions of fluctuating humidity or temperature changes. However, this effect has not occurred in the guitars of that period that have reached Ramírez’s workshop.
Why did the urea-formol varnish cease to be used?
In conclusion, although urea-formol varnish was a popular choice in the past due to its strength and durability, the main reason why urea-formol varnish ceased to be widely used was its toxicity, leading to its decline in use.
The application of this varnish at Guitarras Ramírez began in the late 1960s. They have guitars in their collection from the 70’s with this varnish, and they are impeccably preserved.
Alternatives to urea-formol varnish for guitar varnishing
Less toxic alternatives to urea-formaldehyde varnish for guitars are now available on the market. These include the polyurethane and nitrocellulose systems from Nitorlak.
Polyurethane varnish
Polyurethane varnish consists of a polymer (varnish) with an isocyanate (hardener). When mixed, they react with each other, forming a dry film with exceptional properties for varnishing guitars.
Coverage: It allows good qualities to be achieved with fewer applications.
Hardness: The chemical reaction between the resin and the isocyanate results in a hard polymer.
Flexibility: The choice of resins in the formula allows a polyurethane system with long durability at high film thicknesses.
Adhesion: Provides good adhesion to all types of wood, including tropical and exotic woods.
Chemical and physical resistance: Excellent to withstand wear and tear due to its chemical reaction.
Abrasion resistance: The addition of special waxes increases its resistance to scratching.
High gloss systems: High gloss piano type finishes are achieved with excellent results.
Disadvantages:
Two-component system: Although easy to mix, they always require preparation.
Yellowing: Except if the system is acrylic.
Contains solvents: Precautions are necessary in its application.
The final property of the varnish will depend on the type of varnish and hardener selected. For the varnishing of guitars, polyurethanes with high transparency, coverage and hardness are recommended. All Ramírez guitars are varnished with high quality polyurethane, for years we have trusted Nitorlack as suppliers of paint for guitars, dyes and everything necessary to varnish our guitars.
