Wax is a fatty, solid substance of animal, vegetable or mineral origin. It never gets really dry and is not a durable finish. It will not withstand water, it will turn white.
Wax must be completely removed before varnishing.
Just sanding without first removing as much as possible will clog the abrasive and possibly force the wax further into the wood grain.
Most spay polishes contain silicone. Although easy to apply they can be a nightmare for anyone varnishing as the silicone is extremely tenacious and difficult to remove. It contaminates anything it touches including brushes cloths and even hands which can spread the problem further. Brush cleaning will not prevent contamination remaining on the brush so it can transfer to your next project. Very small amounts can cause problems such as 'fish eyes' in the finish.
WAX OR POLISH ON TOP OF EXISTING VARNISH
If the wax is on top of an existing coat of varnish the task is straightforward as the varnish will prevent the wax soaking into the wood.
We usually use the following method.
Fine wire wool can be used to increase the scrubbing action if required.
1) Clean thoroughly by scrubbing with warm water containing washing soda or washing powder. This step removes much of the wax prior to step 2 but is optional and can be omitted if preferred.
2) Finish off by scrubbing well with a cloth soaked in white spirit. Change the cloth and repeat until all traces are removed.
3) Allow to dry thoroughly.
Other web sites give the techniques listed below.
a) Any old wax or polish can be removed from floors before sanding by initially rubbing with a cloth soaked with white spirit and then scrubbing using steel wool and white spirit. Work the white spirit into the finish to soften it. As the finish becomes softened, lift it using a scrapper (drop the goo either into an old paint tin or onto old newspapers) and then use cloths dampened with white spirit to remove the remaining finish.
Use an appropriate respiratory mask and gloves together with adequate ventilation of the working area as the fumes from white spirit are harmful.
This is messy, but varnish will not cover any of these finishes,
b) Clean thoroughly first by scrubbing with warm water containing washing soda or any good washing powder.
Clean with a rag soaked in turpentine or white spirit.
Unless every trace of wax is removed the new varnish coat will not adhere.
In most cases after cleaning with wax solvent liquid it is well to apply a very thin coat of shellac before the varnish coat is applied. The alcohol in the shellac will penetrate any traces of Wax film on the surface and gain anchorage better than varnish.
Wax left on a surface by the use of liquid varnish removers must also be removed by washing in the same way.
c) To best remove thick wax from wood surfaces, harden the wax as quickly as possible. Hold a bag of ice cubes against the wax to freeze it. Then using an "old" plastic credit card gently scrape the wax off. Metal objects may gouge the surface.
d) Commercial polish removers are sold for removing wax from floors
WAX OR POLISH ON BARE WOOD
If the wax has been applied to bare wood it may have soaked into the wood pores.
Use the methods above, taking care to try to prevent the wax soaking in further.
eg Do not use a hot air gun as the wax will melt and soak in.
In addition to those methods we recommend sanding back the wood at least 1mm.
As we never use wax on bare wood we have limited practical experience in removing wax that has soaked in and would appreciate if any experts can add any expert advice.