Because of the general climate in the UK we don’t see many harps with dryness related problems. But for our customers in other parts of the world and those traveling to differing climates (and even for those living in the UK) a bit of knowledge about relative humidity (RH) and its effect on solid wood instruments is vital to looking after your harp properly.
Our harps are built with wood which has been fully dried to the proper moisture content. The workshop is kept at around 45 to 50% RH and so the harps are nicely conditioned when they leave. The likelihood is that they will not dry any further in the UK (unless subjected to extremes) and are more likely to take on a bit of moisture over time which doesn’t have any effect on them.
40-50% relative humidity is a widely accepted safe range for solid wood instruments. Below 40%, the risk of cracking from dryness begins and the further you get below 40% the greater the risk. Wood loses and gains moisture to match the air around it so if the air is drier than 40% relative humidity the wood will shrink which in turn could make it crack. The longer the harp is dry the more chance there is of it cracking. A few hours out in hot dry weather will not cause damage but sustained exposure to dry conditions may cause problems.
Shrinkage can happen in a few days on thinner wood parts like soundboards and backs and take up to a few months on thicker wood. As each piece of wood is different, there is no way to predict what will happen to any individual instrument. You can rest assured that an instrument kept above 40% RH will not crack from dryness as long as the wood is kept properly conditioned.
It may seem surprising but most cracks develop during the winter in colder climate. Cold air cannot hold much moisture and when you bring that air inside and heat it the RH drops dramatically, potentially right down to 20% or below..
What should I do about it?
The only real way to know if there is a dryness issue where you live or while travelling is to measure the humidity using a hygrometer like this.
The best way to control the humidity is to use a room humidifier that can be set to 40 to 50%RH. This is not always practical and so an instrument humidifier like the Dampit can be placed in the harp to slowly release moisture. Ideally this would be done with the harp in its soft case to close down the environment the Dampit has to hydrate. Even a bucket of water or equivalent in the room where the harp is stored will greatly help.
Building the harp with the properly conditioned wood is as much as we can do to protect it against dryness related problems; once the harp is in your possession we cannot be responsible for its environment. It should be pointed out that in the musical instrument industry it is standard that dryness related cracks are not covered by the manufacturers guarantee.