To successfully apply varnish, it helps to understand valuable parameters. You need to consider things such as the time required for each coat to set, the time to allow between consecutive coats and the reaction to humidity and temperature. The following information will be helpful as you prepare for such a task.
Step 1 - Work in the Correct Temperature
The first thing that you have to observe is that the temperatures in your surroundings are adequate enough to facilitate curing. Generally, varnish won’t cure well if you apply it in temperatures below 65 degrees Fahrenheit. Such low temperatures delay the curing by several days if not weeks.
The best temperature range is between 70 and 75 degrees Fahrenheit. Varnish application in temperatures higher than these is also not advisable as the solvent tends to evaporate too fast leaving the varnish to set prematurely. In such a situation the work quality is negatively affected and you are most likely going to observe uneven films, bubbles, and brush marks on the work surface.
Step 2 - Prepare for the Main Task
Varnish application is very sensitive to the presence of dust. Your application site should be prepared beforehand. If the application is to be done within the workshop, no other sanding tasks should be done simultaneously. If you plan to use another room, begin by mopping the floor and placing the item of furniture on plastic sheeting.
Step 3 - Apply the Varnish
Varnish can be applied in any of three ways: by brush, with a roller and pad, or by spraying. Brushing is a time-tested technique and many high-quality brushes are available.
Although they are costly, the best brushes for the task are those made using China bristles or natural hairs. A cheap but effective alternative is the polyfoam brush, which is disposable. You can buy a Polyfoam brush for each coat of varnish that you’ll apply; they are that inexpensive. You will also be assured of good quality work even with inexperience since these brushes don’t leave brush marks behind.
Step 4 - Apply the Sealer Coat
Before the main varnish is applied, you need to seal the wood’s surface. Fortunately, the varnish itself can act as your sealer. Proceed to thin an adequate amount of varnish to 50 percent by adding either gum turpentine or mineral spirits in a ratio of 1:1. Uniformly mix the two and strain twice into an open container where you’ll be dipping your brush.
To apply, dip the brush into the sealer and let the excess drip off. Proceed to brush it on the wood, along the grain, without leaving any drips or puddles. The item of furniture should then be allowed to dry overnight before you use 320-grit paper to sand it. The number of sealer coats depends on the wood’s porosity. Repeat the process as necessary.
Step 5 - Apply the Main Varnish Coats
Using three or four coats of varnish is the ideal way to get the job done. You should apply these coats in the same manner as the sealer.
The first coat should be applied only after you have cleaned off the sand dust from the wood using either tack cloth or vacuum. Apply the varnish in slow motions to prevent the solvents from evaporating too fast. The item should then dry overnight and be sanded the next day.
The sanding process will indicate how well the drying has occurred. If the sandpaper becomes clogged, then it shows that more time is required for drying. If the varnish becomes powdery, then the next coat can be applied. Apply all the coats similarly and then allow for curing.
This final step to your DIY project is crucial to keep it looking good for years to come. With this guide to applying varnish, it will surely be a masterpiece.