Silicone sealing

earth

Ok, I want to seal around a sink in the kitchen. I've read the guides, watched YouTube. The advice seems to be to squeeze out a bead then spray various liquids over it and your fingers before running your finger along the bead to get it in all the gaps and give it a nice finish. Some people say window cleaner, some say washing up liquid. I've tried both and the bead just came off. The window cleaner people are using is alcohol based but I don't know if the stuff from the supermarket is the same. I've used washing up liquid but not neat (watered down). What's the trick?

Garry H

You can buy a little plastic tool from DIY shops that makes it a bit easier. Use that and washing up liquid. Does take practice though.

earth

Should the washing up liquid be neat or watered down?

rjsterry

earth wrote:

Ok, I want to seal around a sink in the kitchen. I've read the guides, watched YouTube. The advice seems to be to squeeze out a bead then spray various liquids over it and your fingers before running your finger along the bead to get it in all the gaps and give it a nice finish. Some people say window cleaner, some say washing up liquid. I've tried both and the bead just came off. The window cleaner people are using is alcohol based but I don't know if the stuff from the supermarket is the same. I've used washing up liquid but not neat (watered down). What's the trick?

Sounds like there is something preventing the silicone from sticking to the worktop and/or sink. Are these both scrupulously clean? What surface is the worktop and is the silicone compatible with this? Laminate (Formica or similar), hardwood, stone or composite (Corian or similar)?

Also it is a skilled job. There are 'mastic men' who charge a fair rate to do this professionally so don't expect to get it right first time. It's also one of those things that you should apply and then resist the urge to fiddle. If it goes on wrong you are almost better off leaving it to cure, then pulling it off and starting again.

earth

It's an oiled wood worktop. Clean and dry but maybe I should wipe it down with some acetone or something.

rjsterry

earth wrote:

It's an oiled wood worktop. Clean and dry but maybe I should wipe it down with some acetone or something.

Ah. Not sure what the solution is, but I think that is why the silicone isn't sticking.

A quick Google suggests sanding to remove the oil finish, then sealing then re-oiling, but be careful with the type of sealant as some may react with 'fresh' oil.

Garry H

watered down.

Try cleaning with white spirit.

Edit: Ahhh, oil. What he said ^

rjsterry

It does depend how well oiled it is. If you've been religiously applying the stuff every few weeks then it will have soaked in to some depth and you may be on a hiding to nothing.

pinno

Neat washing up liquid to get it to move. If you force the bead into the gap (creating a sizeable body of silicone), it's less likely to move. The washing up liquid is ultra low resistance and really should allow you to smooth it off.

However:

Allow the solvent to dry and make sure the surface is bone dry - use a hair dryer if you have to. At this time of year and with the internal humidity of a house being heated, what you feel as dry might be anything but. Keep the excess to a minimum and once you have an even, continuous bead, run your finger along the whole length of the seal in one action (with detergent) it so that it as neat as can be. I would avoid sand paper and the solvent may only temporarily reduce the oil content on the top 1mm - but that is the window of opportunity.
I know individuals who can run the gun along a gap in a single, even line without needing to manipulate it in any way. It takes a certain angle of cut on the nozzle too. Despite doing DIY for Donkey's, I cannot do that but I can get a finish that is just as good with a bit more effort.
White spirit is probably the kindest solvent to use on the wood.

If all that fails, get Team47b a plane ticket over and he'll do it for you.

capt_slog

What sort of silicone are you using? Is it one that dries (you can wash it off your fingers with water) or one that cures? (smells of acetic acid).

If it's the first one, chuck it in the bin and find some of the second type.

homers_double

Hi mod silicone is what you need, I think it's slightly stiffer than the cheapo stuff.

As pinno says, it's getting the angle of the nozzel right first. Apply your bead and let it go off for ten minutes or so then wet your finger with a bit of spit and gently smooth the bead out. You're not looking to remove any silicone, just evenly spread it.

I have a mate who fits windows and conservatorys so watched him do it loads and he never uses any sprays or treatments, but I agree with the above, it's an art in itself.

team47b

As other have said no need for spray. If you cut the nozzle correctly and hold the gun at 45 degrees the bottom edge of the nozzle touches the surface join and the top edge of the nozzle will smooth the bead as you go and there will be no need to touch it with your finger or coffee stirrer. More than 45 degrees the bead gets squished, less than 45 the bead spreads and you can't control the width. Adjust the speed of application according to the 'quality' of the product.

One I did earlier (bad photo but the silicone is a neater edge than the melamine!)

Finesilver24

Small hole in nozzle
Work away from nozzle and adjust speed to get the correct bead size
Put another 'test' bead somewhere else
Have a pint or 2
When the 'test' bead is 'a bit solid', wet your finger and pull it across the bead to uniformly work it into the join

IF IT GOES WRONG, don't try to recover it. Let it dry , peel it off and do it again.

earth

I'll give it another go soon.