Damp House

[dennis]

Funny, I find them more moist. I don't even need foil unless I am roasting something for hours.

Are you sure you are talking about a fan convection oven and not something else?

[dennis]

Isn't that the fan that blows cooling air through the door space to keep the outside cool?

[mail]

Dear Endymion The symptonms you have described are consistent with condensation. The black mould is likely to be Aspergillus niger. Corners are clasic condensation country due to walls meeting and forming a cold bridge. A 1958 bungalow is most likely to have walls with sufficiently poor U values as to allow condensation. Check your lifestyle and note all the pertinent comments in the posts on preventing water from getting in in the first place (eg put lids on pots when cooking - open windows when cooking and just after baths - do not dry clothes inside - etc etc add to that put some polythene on the oversite next time you have the floors up - increase sub-floor ventilation etc) If that fails buy a dehumidifier with humidistat. It is worth double checking you do not have any hygroscopic plaster as well and if so it will have to be replaced - it is not likely in that age a building Chris George

[Appin]

The message from stuart noble contains these words:

I think we understand that very clearly. The said archive room has no windows, no ventilation to the outside and only one door which opens into another part of the same building which again has no windows and no ventilation to the outside. One outside door from the outer room to the outside. The building is of modern (c 1990) construction 9" block wallls, strapped, insulated and plasterboarded, with approx 9" of insulation in the ceiling, solid (insulated) concrete floors. So relatively little infiltration when compared to the typical domestic situation.

[Dave Liquorice]

I'd have put it a bit lower than that, maybe 30 to 40%, but only from a =

gut feeling rather than knowledge.

You will probably be OK with a moderately airtight cupboard and a heater= . It doesn't take much of temperature rise to make the RH plummet. The outside RH at 0900 today was 65% and the temp 10C. In the next hour the =

temp rose to 15C and the RH dropped to 35%.

Mail order?

Cheap stuff, problem is the P&P will be several times the cost of 100g o= f silica gel...

Or look on eBay 100 x 1g packets for =A33.50 free RM 2nd Class P&P!

Or 8 x 100g packets for =A35.99 + =A33.60 RM 1st Class P&P.

Regenerate it. The 8 x 100g eBay item has destructions for regeneration.= I'd do a bit more research first to check what that seller says but it fits with my understanding. Basicly a low oven for a few hours and weigh= it.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Liquorice" saying something like:

That's the problem - I made an enquiry about buying a bulk lot and it's very cheap per sachet (10p /25g) but the carriage to Ireland is silly.

I've done that - the sales bod I was talking to about up there ^^^ told me there's a finite number of times it can be regenerated and time takes its toll too. I had no reason to disbelieve him - we were in chatty mode at that point and I'd already decided to buy some, it was only later I realised the carriage cost made it uneconomic.

There must be a stockist locally - it's bloody ubiquitous this stuff.

[Dave Liquorice]

Ah, hadn't spoted the Ireland delivery requirement.

I think the number of regenerations is quite high and the time scale qui= te long (provided it's stored in a sealed container once dry otherwise you =

have to dry it again before use)

There must be or at least one in Ireland so you don't get stung by EU postage rates. Tried

though 500g comes ou= t at E17.82 delivered. B-(

I was going to say that CPC is one of those places where it's quite easy= to build up an order big enough to qualify for free P&P but I see that that doesn't apply on cpcireland. Where as on the UK site orders over =A3=

40 ex VAT are free of any "handling charge" for standard delivery.

What do

have to offer?

I'd also be tempted to get the indicator stuff as well, so you know when= it's time to swap out and dry rather than guessing or having to regulary= weigh it.

[Dave Plowman (News)]

You learn something every day. Thanks.

Thought you'd killfiled me?

[Ian White]

I used the same batch for well over 10 years, to fill a drying tube in a system for pressurizing large coaxial cables and outdoor enclosures for electronics. The silica gel in the drying tube typically lasted 2-3 weeks before the self-indicating crystals showed that it needed to be changed; more often in winter, less often in summer.

The stock of activated gel (blue crystals) silica gel was kept in a sealed Kilner jar, and the used gel (pink crystals) was tipped into another container. When the stock jar was empty, all the used gel was spread on a baking sheet and heated for about 2 hours at 180C, then back it all went into the sealed jar for the start of another cycle.

Over about 20 complete cycles there was no noticeable change in its drying performance. The only deterioration was very slow crumbling into finer crystals and dust, which was simply discarded. The stock was topped up from the usual random sachets marked "Do not eat".

It doesn't all have to be self-indicating - a small percentage is enough.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Ian White saying something like:

Useful info, thanks to Dave and yourself. I now have to get moving on it with the end of a wet summer and a probably wet winter coming up.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Liquorice" saying something like:

I had a quick look there, but they're being coy about pricing - not a good sign. There's no way around the steep carriage cost for a decent quantity, so if I can find a supplier somewhere in Ireland it'll probably be cheaper - unlike other things that are usually cheaper to get mail order, the bulky stuff with local use is often as cheap as the UK, just a question of finding it.

[Dave Liquorice]

True but they seem to be more of a producer rather than just a reseller, and they do decent quantities like 25kg drums... or buy far more than you need in packets and flog the rest on eBay with at a mark up to recover some of the costs.

[endymion]

Dear Endymion The symptonms you have described are consistent with condensation. The black mould is likely to be Aspergillus niger. Corners are clasic condensation country due to walls meeting and forming a cold bridge. A 1958 bungalow is most likely to have walls with sufficiently poor U values as to allow condensation.

Thatk you, it is nice to be on first name terms with the mould we are cleaning off the walls here.

Check your lifestyle and note all the pertinent comments in the posts on preventing water from getting in in the first place (eg put lids on pots when cooking - open windows when cooking and just after baths - do not dry clothes inside - etc etc

It is hard to check our lifestyle much more. I have found opening the windows the last few days has seemed to cure the problem a little. The problem with that solution is its cold - although it seems to be colder in than out recently.

Since the sun started to shine and the rain stopped for a while things seem to have improved.

But I cannot think that we make that much water cooking or bathing. Certainly not in cooking. Cooking tends to be by microwave at the moment because I dont want to be in the cold kitchen.

It obviously is condensation though - and a lack of ventilation certainly.

Thanks to all for their helpful comments.

[Rod]

It obviously depends on exactly what you do cook - but it is surprising how much water can come out of a microwave even doing very limited things. As a rule there is nothing to see - but try holding up cold plate near the exhasut fan. (E.g. a plate that you have kept in the freezer for a while.)

And many refigerators remove frost formed internally and evaporate it at the rear using the heat from the coil.

It all adds up!

[geoff]

Are you sure you are not talking about calcium chloride (?) there?

I've never seen silica gel change colour

[Dave Liquorice]

Silica gel itself doesn't but you can get silica gel with added ingredients that do change colour with their dampness. The indicator was cobalt chloride blue (dry) to pink (wet) but that has been found to be a a bit of nasty. So there are now less nasty alternatives, orange to green (organic based) and orange to colourless (iron based).

[<me9]

It often has an indicator incorporated. I've serviced transformer breathers up to nearly 30 years old with the original silica gel, dried out about every three months in a domestic oven.

[<me9]

Just running the hot tap and washing up produces enormous quantities of vapour, you don't need to be boiling anything, just having water above ambient temperature can lead to 100% saturation.

[geoff]

Aah cobalt chloride that's it

[panthers1day]

1:19 +0100, geoff wrote:

Silica Gel will not be colored or change color in it's Original form, which is White/Clear. Some add Chemicals to make it colored and allows it to change color when being absorbed. Stay away from the Blue Silica Gel as this contains a chemical additive called Cobalt Chloride which is NOT something you want near your, your products/food etc.! Cobalt Chloride is linked to cause cancer and the British Chemical Regulations actually requires BLUE Silica Gel to be disposed of as Hazardous Waste!! Just want to make sure everyone knows NOT to use the BLUE or NOT to buy the BLUE Silica Gel. The regular Silica Gel (white/clear) that you find with 98% of your stuff is actually much cheaper then the Blue Silica Gel and can be easily found online (just google Silica Gel Packets and will find several online retailers. Place I use is:

as they ship for free). A good alternative might be using Humidity Indicator Cards or simply replace the clear/white Silica Gel Periodically. Hopefully this will help solve some answers about Silica Gel as well!