Keeping many valuable collectibles dry is the first step to protecting them from assorted other hazards. Bugs -and other destructive living things- need water. Certain destructive chemical reactions are -at the very least- helped on with moisture. Complicated subject and much of it involves too much chemistry. Perhaps the simplest and easiest advice I came across is to put a pound or two of rice in the oven at about 300 degrees for an hour or two. You then put the rice in a shallow tray so it can suck up moisture out of the air. But if you have read my article on bio-hazards -particularly silver-fish, you know that this is a bad idea.

Another bad idea is to use calcium chloride. This is the stuff that they put on icy-roads in some parts of the world. It soaks up moisture very well indeed, but as it does to, it turns to liquid itself -and not any old liquid -it turns to acid. Joan Hammond -the company chemist for the Drierite Company- sez, "This would be trading one problem for a bigger one. It's the stuff that ruins cars."

And this brings us to the smart way to do it. You use a proper desiccant -gypsum -the same stuff they use to make sheet-rock. But this is specially prepared gypsum. One of the things they do with it is to put a chemical in it that changes from red to blue as it gets full of water. When it gets full of water, you have two choices -you either throw it our and start over -and it's not all that expensive- or you put it in the oven -like the rice- and cook it dry and use it over and over again. The water absorbing ability does not diminish, but the indicating chemical wears out. It doesn't actually wear-out -is migrates into the granules of gypsum and gets thin enough on the surface to the point the color change doesn't show. Gypsum -by the way- is completely harmless -have yourself a bowl of it for breakfast. But the moisture indicating chemical is poisonous.

So how to buy and use the stuff? Well, the Drierite Company will be happy to sell you the modest quantity a collector or hobbyist might use. They will also sell you a little aluminum container to keep it in. You can toss the aluminum and the desiccant it holds into the oven when the need arises. Or after baking a mess of 'taters for that matter. (But don't cook the desiccant at the same time as the 'taters -the desiccant will happily absorb the steam from your them as they cook.) Then it depends on your specific needs and the effort you are willing to spend. The stuff is sufficiently innocuous that you could -for example -simply spread some out in the bottom of your case or the back of a drawer. Have to sweep it up when it's done it's job. or you can put it in a little saucer of make a little aluminum foil boat or even sew a little bag with cloth that is porous. For that mater, Dreirite makes little bags with the stuff already tucked away inside. Here is what they say on the subject of how big a bag for how big a space.

SUGGESTED USAGE OF DRIERITE DESICCANT BAGS Volume of moisture tight container

Volume Example (appx.) Bag Size Cu. ft. Cu. in. example
3 grams 0.13 228 half-gallon milk carton
6 grams 0.25 456 gallon jug
1 ounce 1.25 2160 case of wine
2 ounces 2.5 4320 suitcase
4 ounces 5 8640 small filing cabinet
8 ounces 10 17280 refrigerator

Notice the use of the word "tight" when they describe the volume of a given container. You must understand that this table is for things like cameras that are sealed up in a nice plastic bag to be shipped off to market. The desiccant bag pulls the moisture out of the air contained in the bag and the camera gets there with out rust or corrosion. It is NOT expected to suck all the moisture out of the air on the high seas during the trip. What this means to you is that unless your collectible is sealed up in a nice airtight container -you are going to have to -at the very least- keep an eye on things.

But more likely, you will need to replace the desiccant. If your means of containing the stuff allows you to see it, and if you have purchased the indicating granules, then it's a simple matter to tell when you need to put it in the oven. If you have it closed up be it in your own cloth bag -or the ones Dreirite sells you, you can use the cheaper non-indicating desiccant, BUT you will need some means of telling when the stuff has soaked up all the water it can hold. This brings us to......

Humidity Indicators

While you are shopping at the Drierite Company, order some indicator cards too. These are little pieces of cardboard with the indicator chemical painted on the surface. They come in two varieties. One changes from blue to purple when the air is 30% relative humidity or more. These cost about 15¢. The other -cost about 50¢- change a range of colors to indicate the humidity from 10% to 60%. There is a color scale you use to interpret the color and they indicate the changes in humidity for a good long time. They both can be reused when they are given the chance to dry out.

You have to be smart about handling the first cards -if you open the entire package just to look at what you spent your money on -and it's a humid day -surprise!- you will have a bunch of cards appraising you of this fact!

There are a few tricky issues that need some discussion on the topic of desiccants and fine collectibles. First -some items -for example fabric- may not want to be bone dry -makes them brittle and this make them tend to fall apart. Second, it may be that you can close up you collectibles is a reasonably tight container -pull the humidity out with a one-time-use desiccant bag -and as long as it stays in the container -figure you have done your job even though the humidity might raise again. Depends on what you collect, what you are storing it in, where you live and what time of year it is. Finally, and in fairness to my customers, I must say that I make pretty things out of wood and wood has its own issues with moisture content and the environment. Let me stress that I make no claims or warranties about anything to come out of my shop with respect to its ability to seal something up in a hermetic vessel.