Protecting the Finish of Your Harp
There are many fine furniture polishes that work well at protecting the finish on your harp. All of the ones you want to consider have wax in them. Never use furniture oil on your harp as it will cause a build-up on the wood and, essentially, a gunk-up on the hardware and strings. When applying a wax product, put the wax on a rag first; never apply the wax directly to the wood.
Wax products are designed to put a thin slippery protective coat over a finish. In this way acidic sweat and the oil from your hands interacts with the polish, not with the finish itself. Additionally, polishes may slow but can not stop oxidation of the finish or the exchange of moisture between wood and air. Interestingly, no matter what you have heard from advertisers, it is almost impossible to get a “wax build up” on wood if the wax has been applied properly. This is because solvents in the new coat will liquefy the old coat, making a single new layer. (Floor wax build up is another story and is not comparable.) Myths surrounding wax as a dampening agent on wood predate modern polishes and have long ago been disproven.
A good quality furniture paste wax will give you the hardest and most long lasting protection. However, it is very difficult to apply. Paste wax must be rubbed on, allowed to fog/dry and then buffed off until the wax shines. Working around strings, tuning pegs and sharping levers is quite time consuming.
A simpler choice is a liquid polish which can be sprayed onto a polishing rag. Products in this group just need be rubbed on until dry to the touch. However, when these products evaporate the protection is gone. It is a good idea to use them once a week. Professionals that travel and gig everyday may want to polish more frequently.
Liquid furniture polish comes in two forms, a clear liquid or a milky liquid. Since you generally cannot tell the color of the liquid inside the can, select one which says that it contains wax and lists oil as one of the ingredients. The oil combined into a wax product removes oil soluble dirt and water-based chemicals which are also in the product remove water soluble dirt. The clear products, without oil, only remove water soluble dirt. In our shop, as a result of a study done years ago and published in Fine Woodworking, we use Pledge. (We were surprised too.) Pledge is a milky oil distillate product, and it is one of the few liquid polishes that actually contains some wax. Pledge comes in two versions, one with wax and one without. Be sure you selecting the oil-based product with wax if you decide to go this way.
As a final note, perhaps the best reason to keep a polish on your harp is that it makes it slippery and that little but of extra slip can sometimes help if the wood takes a minor blow. If keeping your harp polished helps to prevent a scratch or a minor dent then it is time well spent.