Silicone minefield

In message , R D S writes

I find this very worrying

As an optician, I would have thought that you would have ay least had a basic knowledge (e.g. A level) of physics

or failing that, been able to type it into google

e.g.

I am a lowly dispensing optician, we don't need A levels*, but don't worry about me I manage to get through a day of spec making OK, but do find myself stumped every few years or so when I come to seal my bath. If only there was a friendly DIY group I could ask in, one where people without their heads up their arses could be of help.

I have looked using google, and wading through the vast sea of ads for silicone I read that modulus refers to rigidity and low modulus is rather flexible. This sounds good to me. But then I read that low modulus silicone isn't the best for use in high humidity areas.

Plus, if everyone went to google you would lose the chance to be the group's condescending tit.

In message , R D S writes

Stop moaning - I posted your answer for you

No you didn't. I am still unsure as to whether I would be better off with a different silicone for a bead around a bath.

Anyway as you say I would be better off sticking to google. I asked a simple question and all I have this far is your reply, which was at best irritating.

In message , R D S writes

You could use acrylic bathroom filler or low modulus silicone, either will do the job, all you are doing is filling a gap. Make sure the surfaces are clean and dry and if you are actually sealing a bath to the wall, it's usual to fill the bath so that it and what it sits on are weighted and the silicone doesn't stretch and split every time you fill the bath

Oh, are you an optician too? That's a coincidence I understand the OP is also an optician.

In message , OG writes

then there is a gap in your understanding

I also wonder why you being an optician means the OP should have a knowledge of A level physics.

shear modulus or bulk modulus?

Ian

Funny - I thought the gap was around the bath...

Andy

Jeezus. I must have asked the question wrong.

Is this group full of scientists rather than people who regularly use silicone.

There shouldn't be now - I told him how to do it

Then low modulus is more stretchy and is intended where they may be several mm of movement over the life of the seal. Ideally in a bathroom the bath should not be moving that much relative to the wall/tiles.

You can use the low modulus stuff (it will be softer than santiary silicone). The sanitary silicone may be loaded with more biocides than the stuff you have.

Couldn't have done it without you.

I just happened to apply a new bead of silicon to the bath yesterday as the old one was a bit grotty in a few places and a new shower screen was also going up.

Use a high quality bathroom silicone sealant. Do not use an acrylic sealant these are crap for this purpose.

A low modulus means that the sealant will be slightly elastic. It will be able to stretch a little to accommodate movement when in use.

The standard approach for sealing around a bath is to fill the bath with water to 2/3 - 3/4 of the level you would normally use. If there is any movement in the bath when filled with water, this would roughly put it at about half of the full displacement. Leave the water in the bath for 24 hours while the silicone sets.

Push the sealant into the gap rather than dragging it along behind the sealant gun. There are various tools for smoothing out the sealant that can be a big help in getting a good finish. Alternatively you can also produce a decent finish with careful use of your thumb and a bit of practice, but make sure you wear some decent nitrile or similar gloves that are a good fit. Whatever you use, clean it regularly and dip in water before use.

cheers

David

So, there you go ...

Some years back I wrote a FAQ piece about such things.... not sure if it got added to DIY FAQ but it is on UK SelfBuild..

Take a look at Mastioc & Sealants on