What are thixotropic varnishes and when to use them

Many wood varnishers have encountered the terms "thixotropic", "thixotropic" or simply "thixotropic", referring to a property of varnish. But what does this "thixotropic" mean and when do we need a varnish with such a property?

If we look in the DEX, we find that thixotropy is "the reversible transformation of a gel into a solution as a result of agitation or the action of ultrasound". I'm sure I haven't helped you at all, quite the opposite in fact. However, I think we can use the definition to start the explanation. So, according to the definition, thixotropic varnishes should be varnishes in gel form which, if agitated or under other external action, turn into solution.

But why do we need such a varnish? Because even when the varnish is thicker we need to thin it to apply it properly. The varnish sits well, looks nice and doesn't crack over time if you apply several thinner coats instead of one thicker coat. So why do we need gel varnish?

Because there are situations when we want to apply a large amount of material without applying many coats and without getting defects and problems. These situations occur when the lacquer is applied by spraying and the spraying is vertical.

When finishing a piece by spraying, it can be placed on a stand and applied as in the picture below.

Or it can be hung on a stand, with varnish applied along the length of the piece, from top to bottom.

The same applies to the lacquer on the sides of furniture, and the phenomenon applies to both finishing lines sophisticated factory equipment and for diy projects and makeshift spray booths.

To be able to do this application from top to bottom, vertically, and to get a good result, you should apply many thin layers because otherwise, due to gravity, the varnish would run off.

This is also where thixotropic lakes come in. Being in gel form, the varnish can be applied in larger quantities, without spillage and without problems of film cracking because of the too thick layer of varnish.

Thixotropic varnishes are very useful when applying to chairs, windows, when you want to apply a large quantity without the risk of spills. When using them, follow the manufacturer's instructions otherwise you risk losing this property. For example, in the case of outdoor water-based products, which usually have a very high thixotropy, the recommendation is that the gun has a nozzle of 2.8-3, so that the lacquer can come out of the gun. A smaller nozzle will make the lacquer come out harder and you will tend to dilute it. By diluting it, even if not very much and stirring to homogenize, the gel turns into a solution and you won't be able to apply a large amount of varnish in one pass. Such products are usually applied undiluted and settle very well on the substrate when applied with special pumpso that it can be easily removed from the gun, despite its thickness.

The degree of thixotropy varies, not all lakes are very viscous and need large nozzles. There are also products, such as polyurethane varnishes for example, that have high viscosity but can be diluted to a certain application viscosity and mixed without problems. But always follow the manufacturer's instructions.

A disadvantage of products with high thixotropy is that, when applied horizontally, spreading is not very good and the film may look like orange peel. If diluted further, however, the varnish loses its properties and can also be applied horizontally without the risk of small bumps.

In summary, thixotropic varnishes are used when sprayed vertically. This is the case for industrial finishing of chairs, furniture sides, windows, but also when you have a small workshop where you finish all sorts of objects and don't want to make spills on the corners or sides.