Sooner or later someone, quite often a child, will ask about the mysterious silver button in the museum case. What is it? What does it do? What would happen if you touched it?

I admit to having been one of those kids who spent most of my time in the museum fantasizing about the silver buttons as my parents oohed and aahed over objects that were pretty uninspiring to a seven year old. If I twisted that one over there just so, perhaps some secret wall would open, leading me into a far off land of orcs, witches, and wizards. Or, if I rubbed that one in the case next to the sword, a knight might step forth, inviting me to visit his enchanted castle on the edge of the forest.

It would be more than thirty years before I would really understand the importance of what I called the Silver Button. You see, the Silver Button was none other than a thermohygrometer turned upside down so you couldn’t see its face. And, indeed, it would be the magical world of conservation to which the instrument would ultimately take me.
Simply, the thermohygrometer measures the temperature and relative humidity within the environment in which it is placed. Some, like those I encountered as a child in the museum cases, are silver-like disks with dual hands and gauges. Recording thermohygrometers are large appliances that actually record the humidity and temperature on a minute-by-minute basis day in and day out. Here, graph paper rotates on a drum while a stylus puts down tiny markings as it moves.
Conservators have learned to be closely mindful of the relative and often dramatic effects a rise in either temperature or moisture can have on a given object. A dramatic reduction in either area can have equally disastrous effects, depending on the objects being conserved.

Typically, microorganisms enjoy a free reign in high temp/high water environments. And, when they themselves fail to do harm, it is their waste products that do. In addition, water, being composed of oxygen and hydrogen, oxidizes metal surfaces.

The reverse side of the spectrum is no rosier. Total absence of water in the environment promises dehydration-especially if the temp stays high-and embrittlement or friability. While this state isn’t always destructive in itself, any shock or dramatic disturbance can cause fracture or total disintegration.
By now you’re probably thinking it’s a good idea to purchase a thermohygrometer. Knowing as much as you can about the environment in which your collection is kept is the first step to extending its longevity or its chances for survival. No matter what you collect, whether it’s art, china, ceramic, toys, teddies, Indian baskets, or bear rugs, a thermohygrometer is a necessity.

There are dozens of different makes and models. Usually the price is a clue to the accuracy, but not always. The Silver Button type of my childhood is still manufactured in England but, while the temperature is easy to adjust, the RH or relative humidity is not. Warning . . . Red Alert . . . You cannot adjust the RH of a thermohygrometer yourself without another, much more expensive instrument. So, forget this type for home use unless you know what you’re doing.
The nicest wall instrument features a digital thermometer with an analog needle controlled by a natural hair bundle. The hair bundle responds quickly to the changes in humidity and its quite reliable.
Then there’s the little gray cube. That’s what I call it, and it features three scales: two analog dials, one for temp and other for RH, and a humidity strip you read by color. And, it’s small, measuring about one inch high by two inches long by three-quarters of an inch deep. This one comes pre-adjusted for RH too.
If you write to me here at the magazine I’ll be pleased to let you know where to get a reliable and economical thermohygrometer.

One rather usual compliant we hear is: “I have a huge collection. It’s all over my home. Now what do I do?” The obvious answer is the best you can. This is tougher than it seems. There are conservation scientists who specialize in environmental issues and even they say there are many ways to achieve optimum results. Here are some things to think about;


  • Ascertain the vulnerabilities of the objects you collect. It’s good to think about the basic materials that compose the objects.
  • Keep all like objects together. That way if you keep one room cooler than another similar objects will benefit.
  • Large collections often present several obstacles to good hygiene. The main problem is that once you’ve finished cleaning all the things you own it’s time to start over. So, if your favorite things are, say, teddy bears recognize they attract dust and other airborne particles. This can be compounded if they are handled frequently, because oils transfer from hand to fur.
  • Measure the temperature and RH in different parts of a room before you hang pictures or store objects. You’ll discover the higher up on the wall the dryer and hotter the environment. Can your art or artifact withstand such rigors?
  • Keep good records and photos. Learn to spot problems by reading about the things you collect.


The Silver Button will be your passport to wonderful places. The best being where your collection lives happily ever after.