Silica gel? how does it work?

[matnoo]

Have problems with humidity on my boat, do silica gel sachets work indefinately? Ie do they grab moisture out of the air and then when the airs very dry do they evaporate the moisture back out? Ie, do they act like a huge surface area that moisture likes to condense on?


Or do they chemically react with the water? And in effect get used up?

Mat

 

[allangray3]

Silica gel is a super dry form of sand which absorbs water to its natural water content so does need drying in a warm oven. this is required more often the damper the enviroment. only any good for areas of low air movement eg lockers and cupboards

 

[BrendanS]

No, not indefinitely, they absorb water from the air into the crystals, retaining the water absorbed.

Useful for keeping small enclosed spaces dry, like inside of dry boxes, or small dry cupboards

Absolute waste of time in a boat, as you'd need tens of kilogrammes of the stuff to make an impact, and then you'd have to replace that very regularly

 

[Thistle]

Silica gel is fine for small, enclosed spaces (eg boxes). For bigger spaces (eg boats, houses) some combination of heat and ventilation is a better bet.

 

[Channel Ribs]

There is scope for a Lakesailoring here....

/forums/images/graemlins/laugh.gif

 

[VicS]

[ QUOTE ]
does need drying in a warm oven

[/ QUOTE ] At 110C usually.

 

[ArthurWood]

Silica gel is silicon dioxide in a form which has a huge surface area per gram (about 800 sq. metres) of the material. The structure is something like that of a sponge. Water is ADsorbed onto the surface, not chemically bonded, but physically and can be removed by heating to 150C. As stated above, it's not useful for keeping large areas/volumes dry because it is so very adsorbent. They used to sell pots of the stuff in caravan acessory shops in the UK (we had a motor caravan many moons ago) to keep the vans dry during storage, but the gel (which is not a gel, but granular) saturated almost as soon as you opened the container!

 

[marcusgillies]

salt or rice (uncooked) is the cheapest alternative. we use a mixture the salt helps to take moisture from the air and the rice takes the moisture from the salt. just put in in a bowl and leave it. will need replacing about 1nce a month.
dehumidifyers are ok but most people have them on to high and all they do is drag excess moisture to the boat from outside.