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Silicone on silicone and silicone on pine

May 30, 2019 — BarryK

My education continues! One comment: a lot of information on the Internet is incorrect or misleading. I read yesterday, that silicone sealant will not stick to cured silicone sealant. Wrong.

I tested Selleys 401 silicone sealant, on top of the same sealant that has cured for several days. It bonds extremely well, and I was unable to pull it off. That information on the Internet may be for neutral-curing silicone, or just one type that the author tried, then made a sweeping statement.

Wood is the same story. Some web pages state that silicone sealant will not stick to wood, others say it will. My experience with selleys 401 is that it doesn't, or does so very poorly.

So, I tried Parfix "Roof, Gutter and Concrete" silicone sealant, which is neutral cure, on unpainted dressed pine, also on pine sandpapered with 60-grit sandpaper. In both cases, it suck extremely well, and again, I was unable to pull it off.

I haven't tried, but won't be at all surprised if the Parfix sealant bonds well to aluminium also (which Selleys 401 doesn't). Hmmm, should find out for sure, will do a little test today. Will also test Parfix on cured Parfix! 

Academic papers on tilted wick-type distillers

I have found some practical academic papers, with very useful experimental results:

"Solar Stills for Desalination of Water in Rural Households"

"Experimental study of an inclined flat plate-type solar water distillation system"

"An experimental study on an inclined solar water distillation system"
-- free download, but have to join

There is some very interesting information. For example, one researcher was reading just 60 - 65degC inside the still at high-noon, at external ambient of 25degC. This is still hot enough for evaporation to take place from the wicking cloth.

One researcher used a black bath towel. I had thought that would be too thick, but hey, if they can do that, so can I...

Bath towel wicking cloth

I bought a black cotton bath towel from Kmoart, for just AU$6. BigW also has them, same price, but they have embossing, whereas the Kmart one is just a plain surface.

Tested it this morning, very positive result. Capillary action was observed to be better than the felt, though I haven't quantified that. Just an observation, that the water tended to get absorbed more readily.

The three 1mm holes are working OK. The water is spreading out, and only a few dry spots after 15 minutes, and very little water has made it out the bottom drainage pipe. Excellent, dry spots are one of the problems with this type of still, and it is a matter of correct angle and water flow rate. 

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