\u23f1 Reading time: 4 minutes<\/p>\n\n\n\n
The adsorption capacity of a desiccant is determined in the laboratory by exposing the material to air at controlled temperature and relative humidity, and measuring how much water it retains at equilibrium. The result always depends on the test conditions: the same product adsorbs very different amounts of moisture depending on the climate it is exposed to. This is why the DIN 55473 and MIL-D-3464E standards define fixed test conditions, allowing desiccant bags to be compared on a single, equal basis across all manufacturers.<\/p>\n\n\n\n
Desiccant bags used inside packaging (inside boxes, to put it simply) are generally produced with three desiccant materials:<\/p>\n\n\n\n
As we will see, the capacity of all desiccants<\/strong> varies with the temperature and relative humidity conditions in which they are used<\/strong>, which is why technical standards have been created over the years to regulate their use, production and testing methods. These standards are a useful tool for the customer<\/strong>: in a landscape where extravagant claims about desiccant properties are the norm, they make it possible to understand exactly how to evaluate the various products.<\/p>\n\n\n\n The most active standard today is DIN 55473.<\/p>\n\n\n\n A desiccant has no “absolute” absorption capacity. The amount of water it can retain at equilibrium depends on two variables: the temperature and the relative humidity of the surrounding air. Strictly speaking, it also depends, to a very small extent, on atmospheric pressure, but this can be neglected under normal conditions of use.<\/em> The higher the relative humidity, the more water the material adsorbs. Temperature works in two directions: it increases the capacity of the desiccant but, as it approaches the regeneration temperature of the material, it starts releasing moisture back into the environment, reducing the capacity until it is cancelled out completely.<\/p>\n\n\n\n Same product, same quantity: the figure changes only because the test conditions change. A capacity value without the corresponding temperature and relative humidity means nothing.<\/p>\n\n\n\n In practice, if a manufacturer tells you that their silica gel desiccant bag (a manufacturer of this kind would probably call it a “salt”) is better than the competition’s because theirs absorbs 35 g, it means they do not know, or fail to tell you, that their test was carried out \u2014 assuming they actually ran it and did not just copy figures from the internet \u2014 at a higher relative humidity, and that those 35 g are merely the performance of silica gel under extreme relative humidity conditions.<\/p>\n\n\n\n Standards define the exact test conditions, so that buyers can compare products on a single, equal basis.<\/p>\n\n\n\n Two bags declared as “1 unit” under the same standard therefore guarantee the same minimum performance, regardless of manufacturer or adsorbent material.<\/p>\n\n\n\n The DIN standard also defines how desiccant bags must be packed: another topic we will cover separately, as it deserves proper attention. For now, let us just say that Levosil delivers its products packed in HDPE to prevent them from becoming partially saturated before use, which would reduce their drying capacity. Attention is often focused on performance figures, while how to preserve that performance over time is overlooked. Levosil guarantees a two-year shelf life on its products.<\/strong><\/p>\n\n\n\n Test conditions at low relative humidity are not an arbitrary choice: they measure the water that is actually retained.<\/p>\n\n\n\n Moisture adsorbed at 20-40% relative humidity is stably bound within the finest porosity of the granule and is not released back into the packaging. In contrast, the water absorbed in a test at 80% relative humidity is partly held weakly, through capillary condensation in the larger pores: if the relative humidity of the environment drops, that extra share is easily released.<\/p>\n\n\n\n A value measured at 80% relative humidity is therefore an impressive figure, but it does not represent the real protection the desiccant provides inside the packaging. Before comparing two datasheets, always check that the test conditions are declared and identical.<\/p>\n\n\n\n Besides, you had better hope your packaging never reaches 80% relative humidity, because at that point whether the silica gel performs at 24 or 35 per cent would be the least of your problems\u2026<\/p>\n\n\n\n The same principle applies to calcium chloride desiccant bags used inside shipping containers. Here too, fanciful and optimistic claims circulate on the web and need to be analysed to be fully understood. It is worth noting that the proliferation of “optimistic” manufacturers<\/strong> regarding the performance of their product has been largely encouraged by the lack of an industry standard for these materials.<\/p>\n\n\n\n We will dedicate a specific publication to this topic.<\/p>\n\n\n\n If you want to make sense of all this: 0039 011 96 43 430 \u2014 info@levosil.com<\/p>\n","protected":false},"excerpt":{"rendered":" \u23f1 Reading time: 4 minutes How is the adsorption capacity of a desiccant determined? The adsorption capacity of a desiccant is determined in the laboratory by exposing the material to air at controlled temperature and relative humidity, and measuring how much water it retains at equilibrium. The result always depends on the test conditions: the […]<\/p>\n","protected":false},"author":4,"featured_media":5573,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[111,115,113,114,112,116],"class_list":["post-5575","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-activated-clay","tag-adsorption-capacity","tag-din-55473","tag-mil-d-3464e","tag-molecular-sieves","tag-relative-humidity"],"_links":{"self":[{"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/posts\/5575","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/comments?post=5575"}],"version-history":[{"count":1,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/posts\/5575\/revisions"}],"predecessor-version":[{"id":5576,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/posts\/5575\/revisions\/5576"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/media\/5573"}],"wp:attachment":[{"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/media?parent=5575"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/categories?post=5575"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/levosil.com\/en\/wp-json\/wp\/v2\/tags?post=5575"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Capacity depends on the test conditions<\/h3>\n\n\n\n
Example: 100 g of silica gel in two different climates<\/h4>\n\n\n\n
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The standard is a guarantee for the customer<\/h3>\n\n\n\n
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Why testing is carried out at 23 \u00b0C and 40% relative humidity<\/h3>\n\n\n\n
What about calcium chloride container desiccants?<\/h3>\n\n\n\n
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