Moisture between my plastic cover and my timber garden table

[wotsallthis]

Covering a garden table when the cover is in contact with the table leaves moisture. Apart from wondering why people buy these these destructive things (I hope I've got it right) and

not being a scientist, could you tell me please?

How does moisture get there.

If you are a handyman (Do it-your-selfer as well,

Do you have any ideas?

Keep well everyone.

 

 

 

[exchemist]

1 hour ago, wotsallthis said:

Covering a garden table when the cover is in contact with the table leaves moisture. Apart from wondering why people buy these these destructive things (I hope I've got it right) and

not being a scientist, could you tell me please?

How does moisture get there.

If you are a handyman (Do it-your-selfer as well,

Do you have any ideas?

Keep well everyone.

 

 

 

I think this will be condensation, from periods at which the temperature of the table and cover goes below the dew point of the ambient air. An uncovered table would also develop moisture, but the presence of the cover will hinder its re-evaporation when it warms up and/or the relative humidity drops.

Typically, objects will get somewhat colder than the ambient air at night, as they radiate in the IR. This is especially pronounced when there is no cloud cover, so that there is no balancing IR radiation coming back down from the clouds. This explains for example why you can get a ground frost on clear winter nights, even though the air temperature can be 3-4C above freezing.  So if the relative humidity is close to 100%, a table or other exposed surface may, for a while during the night, have a temperature below the dew point. 

[studiot]

2 hours ago, wotsallthis said:

Covering a garden table when the cover is in contact with the table leaves moisture. Apart from wondering why people buy these these destructive things (I hope I've got it right) and

not being a scientist, could you tell me please?

How does moisture get there.

If you are a handyman (Do it-your-selfer as well,

Do you have any ideas?

Keep well everyone.

 

 

 

 

You might find this about a 'desert still' interesting.

 

https://www.desertusa.com/desert-people/water-solar-still.html

[sethoflagos]

On 8/22/2022 at 8:32 AM, wotsallthis said:

Covering a garden table when the cover is in contact with the table leaves moisture. Apart from wondering why people buy these these destructive things (I hope I've got it right) and

not being a scientist, could you tell me please?

How does moisture get there.

It's already in the wood.

Seasoned wood is typically around 12% moisture at equilibrium, but this shifts around a bit according to the ambient temperature and relative humidity. Since wood (especially softwood) is quite porous, there is a continuous exchange of moisture between the wood and its surroundings. (Reference https://en.wikipedia.org/wiki/Wood_drying)

If you prevent this exchange with an impermeable plastic film, then your likely to find free water pooling under it from time to time.

On 8/22/2022 at 8:32 AM, wotsallthis said:

If you are a handyman (Do it-your-selfer as well,

Do you have any ideas?

Puncture the plastic cover on something like a 5mm pitch to allow the wood beneath to breathe.