Mouldy silicone

[trevorbayliss]

A friends bath keeps needing the silicone changing because it is going black pretty quickly. I changed the silicone for her last autumn and it is black again.

Prior to this the silicone was in for about 1 1/2 yrs and then needed changing.

I have used a good sanitary silicone, so not sure what is happening here.

The shower is over the bath and is set on the long side (not at the bath end). So she takes mostly showers and not baths. There is no leak in the wall as far as i can tell. Nothing coming through on the ceiling.

I was wondering if the grout behind the silicone was the cause of the issue and maybe holding contaminated old or something which is causing the mould to break through quickly.

Any tips on how to sort this out this time ?

 

[just pumps]

What`s the ventilation in the room like?

 

[trevorbayliss]

Good, she has an extractor which comes on with the lights.

 

[JohnD]

and how long does the extractor run on, after the light is turned out?

does the extractor go straight through the wall, or is there a duct?

a photo of the old fan will help.

 

[trevorbayliss]

it is ducted straight through wall, not a long journey.

but not sure of the run time.

 

[Gorners]

Did you use masking tape to apply the silicone? I could be wrong due to the photo not being zoomed enough but it looks like there is quite an edge there where the meets the bath, a classic sign of masking tape being removed after smoothing. That’s where it looks like it’s gone mouldy and will be because water is resting against it and not running away.

If I’m right, and you have to use masking tape, do a final smooth of the silicone after removing - it should still be straight as long as you apply even pressure.

 

[GeorgeNewman]

Hi Trevor,

You might re-apply fresh sealant, but use this product, Dow Corning 785 Sanitary silicone sealant:

https://www.toolstation.com/shop/p5...MI8Z6vpJrB2gIVRrDtCh2jlwl3EAQYASABEgKSWvD_BwE

Dow Corning sealants have very good resistance to mould etc.

George

 

[Madrab]

Tell her to run her towel along the bath edge and silicon seal when she finished drying after a shower in the bathroom. It's purely down to standing moisture, also open that window a crack to get some circulation. Clean the bath seal once a week with a vinger or lemon solution. If it's already in the silicone it needs cut out and re-done.

As george mentions get a high quality anti mould sanitary silicone (just because it's expensive doesn't mean it good quality) ask around but the DC silicone is very good.

 

[trevorbayliss]

Did you use masking tape to apply the silicone? I could be wrong due to the photo not being zoomed enough but it looks like there is quite an edge there where the meets the bath, a classic sign of masking tape being removed after smoothing. That’s where it looks like it’s gone mouldy and will be because water is resting against it and not running away.

If I’m right, and you have to use masking tape, do a final smooth of the silicone after removing - it should still be straight as long as you apply even pressure.

Hey i think this is the reason !! Yes i do use masking tape and yes i think a lip has been formed.

Do you guys use masking tape ? If not how do you get a good finish ?

 

[Gorners]

Hey i think this is the reason !! Yes i do use masking tape and yes i think a lip has been formed.

Do you guys use masking tape ? If not how do you get a good finish ?

Good my eyes are still in good working order

I’ve used masking tape extensively in the past, and still do occasionally, but for the large part I now used this:

https://www.amazon.co.uk/Cramer-40405-5-Fugi-Kit/dp/B003BNLQQ0

Miles quicker and perfect every time - and no lip!

When using masking tape I found applying more pressure to remove the excessive silicone meant I got less of a lip when removing, but I’m not sure it’s even possible to stop it happening completely - I think you can get a thinner masking tape which may help.

My advice is just do a final very light smooth after removing the tape.

 

[Madrab]

Don't use so much silicone, it's a fatal flaw, people aren't sure how much to use and end up using too much and then the dreaded finger smudges it all making it uneven. Using a silicone gun with the correct even pressure and speed along the surface is key & knowing how far up the nozzle to cut depending on the size of fillet that's needed, it certainly is a knack that only comes with practice.

The silicone squeegee's are good too especially for the diy'er if you have a nice flat surface to run along, uneven tiles can be a pain though and can create steps in the silicone.

 

[trevorbayliss]

Ok thanks for the info guys.

 

[Gorners]

uneven tiles can be a pain though and can create steps in the silicone.

This was practically the sole reason for me moving to the Fugi tool, it’s got an attachment that keeps the tool straight across the grout lines so you don’t get the step. It’s a fantastic bit of kit. Much cheaper than it was a few years ago too, think I paid over £20 for it.

 

[Madrab]

The thing to remember, if it isn't right, clean it out and do it again, don't try and keep smoothing it out once it's smudged as it'll never work. If you get it out before the silicone starts to set then it's easy to redo and use a cleaner. Some use white spirit, meths etc, I use the blue brush cleaner. Just have plenty of blue roll to hand

 

[Ian H]

A picture of her in the shower would help get a scale on the photo.