Drying Seed with Color Indicating Silica Gel

P.O. Box 460,  Mineral, VA  23117
Phone:   (540)-894-9481  Fax: (540)-894-9481

©  2011 Southern Exposure Seed Exchange


Color indicator silica gel can be used to dry seed for long-term storage. It may also be used to dry flowers, cameras, tools, shoes, clothing, historical artifacts, display cases, and electronic instruments. It may be used to protect valuable items from mold, mildew, rust, and corrosion. Please read all safety precautions before use.


  • To dry seed, place equal weights of seed and silica gel together in an airtight jar for 7 days. A muslin bag, piece of reemae, or other permeable cloth may be used to keep seed and gel separate inside the airtight container. Use a small container in relation to the amount of seed, to insure faster, more thorough drying.
  • After the seed has dried, remove it from the drying container and store it in an airtight container such as a Seed Saver Vial™, barrier pouch, or any jar with a rubber gasketed lid.
  • When used as directed, silica gel dries seed from 12% typical moisture con­tent to a desired 3 to 5% moisture content. Note: legumes should not be dried below 6% moisture content; otherwise the seed may become “irreversibly dormant”. This means that although the seed is technically still alive, it may not germinate. Legumes can be removed from the drying container after 5 to 6 days. Do not dry any seed longer than 7 days.



Silica gel is a beaded form of amorphous silicon dioxide. In its crystalline form, silicon dioxide is the main component of quartz and of most clay. Clear silica gel (without any color-indicating compound) is packaged with many foods in small packets labeled “do not eat.” About 40 g (1.4 oz) of silica gel will absorb the moisture from three cubic feet of air.

We sell orange-to-green indicating silica gel that also has phenolphthalein at 100 ppm. Phenolphthalein has been a common laxative at much higher concentrations than 100 ppm, but it is being removed from laxatives due to concerns that its consumption at high doses may increase the risk of cancer. The phenolthalein causes the gel to be orange when completely dry, and dark green when saturated with moisture.

Cobalt chloride, the color indicator most blue-to-pink indicating silica gels, poses a more relevant risk of carcinogenicity, as 1) it is used in silica gels at higher concentrations, 2) potential risks occur at lower concentrations, and 3) cobalt chloride may cause cancer when inhaled as a component of dust. Cobalt chloride is no longer allowed in silica gels sold in the European Union, which has led manufacturers to create alternative color-indicating silica gels such as this one.


Set the oven for 250oF.  Spread a single layer of silica gel beads over a very clean cookie sheet and oven-dry for 3-4 hours.  We recommend reserving a new cookie sheet for the purpose of drying silica gel, to avoid absorption of residues from baking.  You may also use a very thick Pyrex glass dish, about ¼ inch thick, with caution.  You may experiment with shorter drying times; however, the gel will appear green as long as it is hot.  Compounds absorbed during use may cause a slight odor while drying.


  • You are responsible for the safe and proper use of this product.  The MSDS sheet supplied by the manufacturer is available on our website, linked to the silica gel descriptions.
  • When transferring silica gel, take care not to spill beads. Beads can be hard to see and easy to slip on.
  • Silica gel gets very hot during the re-drying process. Do not attempt to handle hot silica gel, or any glass container of it, until it has cooled to a safe temperature. We do not recommend moving hot silica gel. If you must move it while it is hot, use a hot pad. Be aware that glass may shatter if it is of the wrong type, is too thin, or is unevenly heated.
  • Do not overheat the gel. Slightly higher-than-normal drying temperatures, such as 280 degrees, are unlikely to overheat they gel; however, overheating can ruin it, and it will take longer and longer to regenerate the gel.  It is better to under-heat it, than overheat it. Do not spread more than one layer of beads over the surface of the container while drying, as this could result in uneven heating.  A good indication of overheated silica gel is the presence of unusually dark or black silica beads.
  • Do not transfer re-dried silica gel to another storage container until the gel has thoroughly cooled. If the gel has not cooled youÂ’ll notice the presence of condensation on the walls of the storage container. Canning jars make good containers for storing silica gel.
  • The drying effect of silica gel can also dry the skin, eyes, and mucous membranes. Avoid contact with eyes and mucous membranes. You may wish to use gloves and/or goggles. In case of accidental ingestion, drink plenty of water.
  • Long-term exposure to silica gel dust may cause lung damage. Under dusty conditions, the use of a mask is recommended.
  • We do not recommend using any color-indicating silica gel to dry foods.
  • Our website product descriptions for silica gel link to the manufacturerÂ’s Material Safety Data Sheet.
  • Certified Organic Users should check with their certifiers before using this product.