Winter temperatures and the quality of the varnish film

I thought it would be a good time for a seasonal article, so I'll tell you a few things to keep in mind when doing winter wood finishing. Why would this be important, assuming we're not working outside in the snow? True, you work indoors, maybe even at the recommended temperature of 18-20 grd.C, but the finishing materials and furniture are transported from place to place, or stored in various places where they quite rarely reach that temperature. That's why I'm still going to make a few recommendations, and they are also valid in case you propose some DIY projects during this period.

If you work with water-based products, you should know that they can no longer be used if they freeze. This applies to water-based adhesives as well, not just varnishes. It is important to make sure thatStorage their temperature is above 5 grd.C. What is confusing is that if they have frozen, after thawing the appearance of the varnish in the container does not change. But during application, defects appear which damage the film. The most common is the appearance of "stars" all over the surface of the object. The film looks like a piece of glass on which a ball has fallen. There is no cure for the defect, the only way to solve the problem is to remove the coating and refinish.

Every time I had the opportunity I said that to get a quality finish, the temperature of the object to be finished, of the finishing materials and of the environment must be close to each otherand not less than 15 grd.C. Failure to do so may result in problems of poor adhesion to the substrate or defective film. Finishing products are tested at a temperature of 18-20 grd.C, the temperature at which they have maximum potential. So, you can have a very good product, but not get the quality you want because the working temperature was not respected. If the wooden objects or finishing materials are stored at lower temperatures, they need to be brought to the finishing site early to reach ambient temperature.

Finishing materials have higher viscosity at low temperaturetherefore more solvent (water or organic thinner) will be needed to reach the required viscosity of application. More solvent means a smaller body (less solid substance) and therefore a lower film quality. More coats will be needed to achieve the desired quality, which will increase the price of the workmanship and therefore the production cost. In addition, for solvent-based products, the emission of volatile organic compounds (VOCs) will be higher.

Humidity wood balance used in furniture manufacturing should be in the range 8-12%, and for wood used outdoors (windows, windowsills, decking, etc.) between 12 and 15 grd.C and should be controlled both on the surface and inside the wood. Even with this humidity, solid wood still works over time and this is accentuated by the ambient temperature. Large temperature differences between outside and inside, or even between work spaces, can accentuate movement. If the products used for finishing are very rigid, there is a risk of cracks in the lacquer film. It is better for solid wood finishing products to be more elastic.

Drying of finishing materialscan also be a problem in winter. At lower than recommended temperatures, drying, especially deep drying, will take longer. It can be forced, but only in specially configured drying tunnels. In these tunnels the temperature rises and falls progressively and the air currents are designed so as not to damage the film. If the drying is forced by placing the finished parts in front of heat sources (such as an aerothermal), the film is damaged and bubbles, cracks and orange peel appearance can occur. More volatile thinners can be used to speed up drying. In the case of water-thinnable products, drying can be accelerated by increasing air circulation in the area. In fact, with hydro products, air circulation is more important than temperature.

Cold weather doesn't mean that work should stop, but it doesn't mean that work should be done anywhere and everywhere. Solutions must be found not to work at temperatures below 15 degrees Celsius, because the risk of finishing defects is very high. And fixing them could cost a lot more than heating a workspace.