Help!: Can't get water tight seal with silicone

[simbob]

Help! Is there some magic art to silicone sealing? I've re-sealed the same area behind a sink twice now and still the water gets through. Sink is set in a standard laminate top, but the wall panel is veneered MDF (hence the need for a good seal) coated with polyurethane varnish, but it's the laminate on the horizontal surface that is the problem.

Initial prep consisted of much wiping down of the area with propanol alcohol (decorators wipes). It was left 24 hours before being subject to water, 1st time i did quite a small bead, second time i doubled the thickness. I can only think maybe it's the silicone i used, which was just an own brand one - is there really any difference between the branded ones and DIY stores own?

Tips, tricks, advice or magic spells welcomed, thanks.

[jay]

Hi is it silicone or mastic

[simbob]

Pretty sure it was silicone, i always thought they were one and the same! It was clear, don't know if they're both available in clear?

[jay]

wipe the area with a dry clean rag or cloth then get some quality silicone and try again it may have something to do with the wipes you are using or it might just be cheap silicone ,hope this helps

[Del W]

Hello, was it in date.They have a shelf life.

[simbob]

Yes was in date, i think it was EVER BUILD Branded thinking about it, what brand is considered 'Quality' Silicone?

[Del W]

Not used ever build. have used mapei from tile giant and unibond range with no problems.

[Stewart]

Everbuild is rubbish in my opinion. Use Mapei, Dow Corning or my favourite, Sealux. As Jay said, the wipes could be leaving a resadue and not allowing the silicone to take hold, so give a good clean down with a dry cloth....


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[simbob]

Thanks guys, will try some new sealant, are any of the 'tools' any good? never tried them but the chap who did the conversion work had a pocket full of them, mostly he'd made.

[peteablard]

I tried cheap silicone once, never again! It costs you more in the long run!!

[jay]

Thanks guys, will try some new sealant, are any of the 'tools' any good? never tried them but the chap who did the conversion work had a pocket full of them, mostly he'd made.

can i ask why he didn't do the silicone for you

[simbob]

I bought the property unfinished from a developer friend and i put in the new kitchen myself.

[simbob]

will bear in mind for future, i always feel i'm being screwed on branded stuff in B&Q

[jay]

sometimes its cheap for a reason ,let us know how you get on

[Rich]

Looks like you have been given the advise you need. Agree with the guys above, use a decent silicone and make sure the surface it totally clean, you can give it a wipe with meths (this evaporates and leaves no residue like white spirit).

The silicone profiling tools are brilliant if you get the right ones, I have tried the cheap ones from DIY sheds and they are not worth a penny but the flat card shaped ones you can pick up from trade tiler are brilliant!

[goodfellow]

You should get a good seal if you can manage to get a bit of sandpaper into the non visable area of the sink (where you are sealing), try to rub it a bit to give it a key and then clean it up with meths to remove any greasy patches and grit, let it dry out thoroughly, perhaps helped on by a hair drier. Then apply a premium quality sanitary silicone.