• Home
• FAQ

FAQ

Silica Gel Knowledge:

Q: What is a desiccant and what does it do?

Desiccant is a hydrating agent, which attracts moisture from the atmosphere. It adsorbs and holds Particles of water to itself.

Q: What is Silica Gel?

Silica gel is form of silicon dioxide, Si02, the material that occurs in nature as sand. The difference between silica gel and sand is that sand is a crystalline, non-porous form, whereas silica gel is non-crystalline and highly porous. Silica gel is synthetically manufactured from the chemical reaction between sodium silicate and sulfuric acid. Silica gel is an amorphous adsorptive substance with stable chemical properties and has a highly complicated porous structure. It is odorless, tasteless, and non-toxic, and offers an excellent capacity for physical and chemical dehumidification because of good absorbability, chemical stability, wide surface area and higher mechanical strength. Therefore, silica gel is used for packing food, pharmaceuticals, goods for export and precision instruments. Silica gel is easy to handle and silica gel saturated with moisture can be regenerated to offer new moisture protection by simply reheating under specified condition. 

Q: How are desiccants best used?

To be used most effectively, desiccants should be used within a closed/sealed moisture barrier. 

Q: Who are our customers?

Electronic Parts, Computers, Pharmaceutical, Packaging, Metal Parts, Engineering Food Packaging, Clothing and Manchester, Chemical and many more 

Q: So silica gel, it’s not really a gel then?

No, silica gel isn't a gel like a hair gel. It is a solid material that comes in granular or beaded forms. These granules or beads are sorted according to their size. For silica gel in sachets, the grain size is not usually important, but for uses such as drying flowers, a fine grain silica gel is more suitable than a large grain silica gel. A 0.5 -1.0 mm grain size rather than a 1.0 - 3.0 mm or 3.0 - 6.0 mm grain. The larger grain sizes are suited for dynamic drying applications where air is dried by being passed through a bed of silica gel. 

Q: But, does silica gel get wet as it adsorbs water?

No it doesn't, one tremendous asset of silica gel is that it traps water molecules inside its pores yet remains totally dry and appears physically unchanged. It does not swell or change shape.


Q: So, silica gel is a desiccant then?

Yes, it adsorbs water vapor by physical means, not a chemical reaction. Water vapor is attracted inside the silica gels crystalline structure.

Q: So, does silica gel now come in many colors?

Yes, now it does. Silica gel comes in either non-indicating or self-indicating forms. Non-indicating silica gel is white and stays white as it adsorbs moisture. Self-indicating silica gels have traditionally been impregnated with a moisture sensitive cobalt chloride indicator. This gives a blue silica gel, which slowly changes color as it adsorbs moisture until it becomes pink. New self-indicating silica gels feature a number of other colors (because they have different moisture sensitive indicators), but all have the same purpose to indicate when the silica gel is saturated and unable to take up any more moisture.

Q: Does silica gel come ready to use?

Yes. The silica gel does not need to be 'generated' before use. It is always sold (loose or in sachets) in a dry condition, ready for use.


Q: How long can silica gel be stored?

Almost indefinitely. The key to retaining sachets usefulness is to keep it under air tight conditions until it needs to be used. Silica gel will adsorb moisture from any environment, so a sachet left out in the open will immediately start taking up water vapor. Although the moisture uptake rate is not fast, small sachets can be vulnerable to such exposure, as they do not have large moisture holding capacity. It is recommended that they are not left open to the atmosphere for longer than 15 minutes. Larger sachets should not be removed from there packaging more than 1 hour before they are required for use. The shelf life of silica gel in a sealed environment can safely be said to be between 18 and 24 months. Practical experience has shown that it can often far exceed this.

Q: How much water vapor can silica gel hold?

Silica gel will adsorb up to 40% of its own weight in moisture.

Q: Can silica gel be used anywhere?

Theoretically yes, but it is really only effective in an enclosed environment. In a situation where new air (and moisture) is constantly being introduced, an unpractical amount of silica gel will likely be needed to keep the Relative Humidity at low levels

Q: What is Relative Humidity?

Air will always contain water vapor. At any given temperature there will be a saturation point at which no more moisture can be retained (any excess will condense). The Relative Humidity of air is the actual moisture content expressed as a percentage of this saturation content. The aim of using silica gel is to keep the Relative Humidity at levels below 50% of the saturation capacity. At these levels, corrosion and mould growth will not be promoted. Problems are often caused if the temperature drops as the saturation content of air at the new temperature becomes much lower. 

Q: Is silica gel dangerous?

Silica gel is non-toxic and non-flammable, it is very inert with a very high melting point. It is very much like sand and thus can safely be sent by any means of transport. 

Q: How can silica gel work when it's inside a sachet?

The materials used to make silica gel sachets are specifically chosen to be breathable. Water vapor passes through them to be adsorbed by the silica gel.

Q: Why are there so many different size sachets?

The larger the item that is being protected, the more silica gel is needed. A range of sachets allows for a single sachet to be used in most cases.

Q: And which size sachet should I use?

It will depend on the application. For a well-sealed item, a rule of thumb is that 10 grams of silica gel is needed for every 30cm cube of volume of the package. This converts to 340 grams per cubic meter. Can you get non-indicating and self-indicating silica gel sachets? Yes. The orange self-indicating silica gels can be seen through the sachet material.

Q: How is silica gel regenerated?

Self-indicating silica gels when they have become saturated can be regenerated by heating at 100-120°C until they return to their original colors. The heating literally drives off the adsorbed moisture. Regeneration can be carried out repeatedly, although eventually the crystals will lose their colour and 5% of their absorption ability after each reactivation. When regenerating self-indicating silica gel sachets, only the minimum necessary heat should be used. Any bags above 10gm the silica gel really needs to be removed from its packaging as the seals can open during heating. Although non-indicating silica gel can be regenerated in exactly the same way, it is not apparent when the silica gel is regenerated other than by checking its weight. it will return to its original dry weight when completely regenerated.

Q: How to Calculate the Number of Oxygen Absorbers Needed? Please click:

silicabags.com.au/oxygen-calculator/

Q: What is an Oxygen Absorber and How Does it Work? 

A: An oxygen absorber is a small packet used to remove oxygen from sealed environments, bringing the oxygen level down to less than 0.01%. 

Unlike silica gel, which targets moisture, oxygen absorbers specifically target air exposure to prevent oxidation, mold growth, and insect infestation.

Most standard oxygen absorbers contain iron powder. When the packet is exposed to air, the iron powder undergoes a chemical reaction—essentially a controlled rusting process—that traps the surrounding oxygen molecules inside the packet as iron oxide.

A: When goods are sealed for long-term storage or transit, trapped oxygen causes three major types of damage:

1. Oxidation: Causes oils and fats to go rancid, changes food flavors, and degrades certain plastics or chemical compounds.

2. Aerobic Mold & Bacteria: Most molds need oxygen to survive. Removing the oxygen halts their growth entirely, even if some moisture is present.

3. Pest Control: It eliminates insects, larvae, and eggs hiding in organic products without requiring toxic chemical fumigation.

A: Yes, this is completely normal and safe. In fact, it means the oxygen absorber is working exactly as it should!

Oxygen absorbers (deoxidizers) contain iron powder. When you open the outer vacuum-sealed packaging, the iron powder is exposed to oxygen in the air for the first time. This triggers a chemical reaction known as oxidation (essentially a rapid, controlled rusting process).

Because oxidation is an exothermic reaction (a reaction that releases energy), the packet will naturally warm up as it actively pulls oxygen out of the air.

A: While the heat is normal, it means the packet is using up its capacity. To get the best results, follow these three steps:

• Work Efficiently: Try to place the oxygen absorbers into your final product packaging within 10 to 15 minutes of opening the main bag. The longer they sit out in the open air, the hotter they will get, and the less absorption power they will have left for your product.

• Reseal the Unused Packets: If you opened a large master pack but only need a few, immediately place the remaining packets into an airtight glass jar or heat-seal them back into a high-barrier foil bag. Once you cut off the oxygen supply, the reaction stops, they will cool down, and they will be preserved for future use.

• Avoid Over-Stacking: When working with multiple packets, spread them out flat on a tray rather than leaving them in a big pile. Stacking them traps the heat, which accelerates the reaction and wastes their capacity even faster.