One of our workshop participants recently asked a question about whether DampRid is safe for use in collections areas. Here’s what the website (http://www.damprid.com/faq) has to say about the product’s contents: “DampRid is a non-toxic inorganic mineral salt named Calcium Chloride. As with all other household chemicals, DampRid should be kept in areas out of reach. DampRid does not emit any type of fume, gas or vapor of any kind.” Please share any knowledge you have about whether this product is preservation-appropriate for spaces without systems that can effectively control RH.
I use DampRid all the time, just not in a collections situation. It is very effective at controlling moisture in small areas. To use it in a larger area you would need a significant quantity. There wouldn’t (or shouldn’t) be a risk to collections. Calcium Chloride is generally safe and can be found in many applications, including as a food preservative.
I must take exception, as I imagine other conservators will, with the statement that calcium chloride is not a risk to collections. It has been found to pose a significant risk when used in proximity to collections museum collections. Calcium chloride strongly attracts water molecules in the air and solubilizes rapidly to form ionic solutions – even at a microscopic level. one of its purposes in industry is to create microscopic surfaces that stay continuously wet and conductive – road salt as the prime example. Ionic solutions are HIGHLY reactive – initiating corrosion in metals, hydrolyzation in skins, leathers, feathers and other protein materials such as gelatin photographic emulsions, denaturating chemical dyes in costumes, textiles and documents . It is also highly abrasive as a fine powder. The desiccant satchels containing commercially available calcium chloride are designed to be generally permeable to water molecules but fine enough to prohibit large quantities of calcium chloride out. That said, the crystals inside the satchels continually break down in to finer and finer particles and will escape as dust particles of the size that suspend easily in room-air convection currents. Where ever convection currents slow – on and under shelving or within cabinets or drawers, these particles settle on whatever material is sitting on those shelves. Where they settle, they immediately initiate accelerated chemical reactions that damage many collection material surfaces. This is not a material you will want to use in conjunction with museum material storage.
Perhaps this discussion should change focus to what IS recommended to deal with unwanted dampness. In order to do that, we would need to know more about what the problem is – why the space is damp, what the negative consequences are for the collections, etc. Relative humidity issues are very specific to the details of the situation; high RH levels are not necessarily bad for every kind of collection, but actual drips or standing water is another matter.
A mechanical humidifier is sometimes useful but a better long-term solution might be to move the collection if it is really at risk or to stop the entry of water at its source. Improving the building envelope is a lot better than measures that have to be monitored constantly.
At Shelburne Museum, we apply a calcium chloride solution to our dirt roads once every one or two years to control dust and it works well for that purpose. We keep it well away from buildings as it can leach up into bricks or porous stone building materials. I agree with Dale that it would not be safe to use inside collection buildings. It will only work to control humidity in small sealed spaces and silica gel sealed into “tiles” is a safer, more controllable, and probably more effective product to control humidity in microclimates.
Barbara, I don’t have a specific situation to report, other than many of the institutions in our NC C2C community have problems with controlling RH levels, esp. in the summertime. At our workshop we pass out silica gel packets, discuss their use in creating a microclimate, and that’s how the question came up about DampRid. The participant has used it with success in her personal spaces but not in collections.
I really appreciate the wisdom you all have shared here (Dale’s points about dust and accelerated chemical reactions, in particular) and have passed it along to our workshop group. Thanks!
If you have a facility wide RH problem you may want to consider renting dehumidifiers to supplement your permanent system for the summer months.
To Adrienne Berney
My business partner, Paul Himmelstein, will be in Raleigh for the SEMA meeting at the end of March to talk about museum lighting. If you want to put together a group, I’m sure he would be happy to talk about RH control.
Barbara Appelbaum aandh@mindspring.com, 212 666-4630
Barbara Appelbaum 5 months, 1 week ago.
