I read that left over silicone sealant can be kept usable by storing it in the fridge/freezer - can't remember which one. Has anyone any experience of this, I hate to throw half used tubes away? Thanks Brian.
Never had a problem keeping silicone, at least for a year or two. Nozzle may need cleaning out, but you can buy spare ones very cheaply from ScrewFix.
Polyurethane (eg SikaFlex) is a different matter, and about 3 months is the maximum I've achieved. Polysulphide ( such as LifeCaulk) seems to stay OK for ever. Guess it depends on whether it's an air-curing or moisture-curing sealant.
A fridge can be very useful for storing glues etc. However I have used a simple method that stops silicon rubber setting for over a year. However, I have not tried this where the tubes are fitted with the newer, screw on storage caps.
When fitting the tapered nozzle make sure that the thread is sealed with rubber to make it airtight. When you have finished, slide another nozzle on top, fill with rubber, then seal the exit hole with a finger, and contimue pumping until there is no air. Push down hard to leave a thin film of rubber separating the two nozzles. A year later you should find the rubber in the outer nozzle set hard, but the inner nozzle is ready for use.
Doug, we use poly-urethane and silicone elastomers on a semi-regular basis at work. These commonly available elastomers require air-borne moisture to activate a curing process. Provided moisture can be COMPLETELY REMOVED from the air, the curing process will stop. Huldah's suggestions make good sense as air-borne moisture has much farther to permeate through an extremely narrow cross-section. Our experience is that moisture can also get in from the back of the cartridge.
Placing the part-used tube or cartridge in deep-freeze definetly prolongs storage life because air-borne humidity is very close to zero. Especially if the freezer is not regularly accessed. The effect of opening and closing the freezer door allows air-borne moisture to enter.
The real trick is to store the stuff in a completely moisture free environment. Some suggestions are:
Place cartridge in a container, with a drying agent like amorphous silica, vacuum contents, and seal with a high integrity seal.
Place contents in a container with a drying agent like amorphous silica, fill with inert gas such as nitrogen, argon or CO2 and seal with a high integrity seal.
In both cases store the container in deep-freeze.
Hope this information helps.
To keep unused sealant fresh, here is two ways.
The first is to smear some grease or vaseline around the top to stop ait from getting into the nossel. This tip was given to me by a round the world sailer, and it kept his silkaflex workeable for 3 years.
Another way is to take a bit of pvc pipe a bit longer then the sealant tube+nossel plus two endcaps. One end is glued the other is used as a cap.
You fill a bit of water in the pipe, enough to cover the nossel, when put upside down. This should stop the air from getting to the sealant. This has worked well for me. If you use 40 mm pvc pipe, it will just fit.
This idea came to me when I was thinking about it, havn't tried it yet, maybe someone can have a go at it. I will soon.
Get a small tin and melt some candle or beewax in it. Seal the top of the nozzel by dipping it in the melted wax a few times to build up a thick coating.
This should stop any air or moisture from getting in. What do you think.
Let us know how you get on. You may have to seal the hole in the nozzel with
a piece of wood first.