TYPES OF SEALERS
WHAT MAKES UP VARNISHES?
In essence, a varnish is basically a paint without the pigment. The majority of these are polyurethane based resins and are solvent based. Acrylic varnishes, although water based, are becoming more popular for their environmental and health benefits.
THREE MAIN CONSTITUENTS TO VARNISH
- Varnish Oils
This is the ingredient that will cure and / or harden on exposure to the air from the protective coating that a varnish provides.
This is the component that adds the strength and body to the finished varnish.
This is the ingredient that thins the oils and resins to allow the varnish to be applied easily.
DIFFERENT TYPES OF VARNISH FINISHES
Varnishes can come in Gloss, Matt and Satin finishes. This describes the sheen of the finish and how reflective it will be. Gloss is the shiniest and smoothest, while Matt describes a dull and un-shiny finish.
HOW A VARNISH HARDENS OR CURES
- Immediate Hardening
Some varnishes harden immediately after the solvent evaporates.
- Gradual Hardening
These are varnishes where there is an ongoing reaction between the oils and resins after the solvent has evaporated.
The biggest factor under our control is the temperature and humidity, so this is worth considering. Read the instructions on the specific varnish you’re using for further guidance, however as a general rule of thumb higher temperatures and lower humidity will speed up curing times.
DIFFERENT TYPES OF VARNISHES
- Acrylic Varnish
These are quick drying and non-toxic water-based varnishes which generally have good UV resistance meaning that they can be used inside and outside.
- Exterior Varnish
These varnishes have been specifically formulated for use outdoors. They have added UV protection so that the wood beneath the layer of varnish is protected.
- Polyurethane Varnish
These varnishes give a really hard surface and are often used for floors and areas which are going to get a lot of wear and tear. They are also heat resistant and will give a clear, tough finish.
- Marine Varnish
This was originally designed for use on boats where the primary purpose was to ensure that water did not penetrate to the wood. To achieve this the varnish must be highly flexible. A rigid, inflexible varnish will crack as the wood bend and flex under the strain of the sea and these cracks could allow water to penetrate.
- Alkyd Varnish
Most varnishes will contain an alkyd of some kind. They are modified natural or vegetable oils.
- Drying Oils
Again, not a varnish, but simply the oils ingredient of the varnish without the resin and solvent.