Removing old silicone :(

[Lobster]

Ye Gods, this has to be one of the worst jobs...

Despite having managed to ignore SWMBO's bleating about the nasty black mould on the silicone seal in the shower for, well, years? I now have no option but to rip it out and redo it, since we have 'damp-patch-on-hall-ceiling syndrom' and I can only suspect the seal is the culprit.

So I'm currently hacking away at it using a combination of Stanley knife, a bare Stanley knife blade, and scraper (which includes a Stanley blade). It's leaving bits behind and in the gap between tile and shower tray; and I can't help feeling that where I've slashed at the stuff it will make future leaks more likely if I can't get 100% of it out. I'm also nicking and scratching the acrylic surface of the shower tray which isn't great.

Any wonderful tips on how to do this job properly? Are the silcone-eater-type solvents any better than they were 10 years ago when I last tried them (useless)?

Do I need to get every last trace of silicone off, or will it be OK providig all the black s**te has gone and I'm back to cleam, solid substrate before applying new stuff.

And what about tips to avoid mould growth in the future? I've bought a sanitary grade mould-resistant silicone to replace it with - but I'm pretty sure that's what I used originally :(

David

[Hugh - Was Invisible]

Silicone is not great at sticking to silicone. You need plenty of clean surface to stick it to.

I used Unibond silicone sealant remover which did a reasonable job but costs. Hopefully someone will be along with better suggestions.

So far as I am aware silicone can always get mould eventually and does not last forever anyway.

[harryagain]

I have been told that silicone beads should not be too thick or it is not stretchy enough and it will fail and leak. Also you need the proper sanitary sealant. (More stretch than other sorts.) Also put a heavy weight in the shower tray to open the gap to maximum before applying the silicon. Leave there 'til it sets. Reduces movement and chances of a leak.

[Lobster]

Thanks for the reply Do you reckon that's any better than other similar products? Have just looked it up on B&Q#s website where it has three user reviews, all of which are uninspiring:

"I wanted to purchase the B & Q own brand as it had a much better review. They only sell this one at my branch. Those who expect little shall not be disappointed, I scrapped most of the mastic off before applying this, just to get rid of the stubbon stuff, it took two goes. It did help a little. I cannot understand why a small branch would sell the inferior one instead of the five star one especially as the five star is the own brand. It defies logic."

"Do not waste your money. I followed the instructions and all that happened was I had a lot of sealant remover to scrape off and was left with most of the sealant still there. There has to be better products out there. This just does not work!!"

"Totally useless. We bought this to remove the silicone sealant from the back edge of the kitchen sink as the original was mouldy. Previously we would have used a Stanley blade to start an edge then pulled out the old sealant. Not only did this alleged sealant remover not do any removing, it made it harder to get out than if we'd not used it in the first place. We followed the instructions on the tube to the letter and would certainly not buy this product again, it is worse than useless"

Sounds pretty similar to the results I got years ago with another agent... :(

David

[JTM]

As Hugh + Harry say, the remover is poor, but I think when I left it on looong time it *seemed* to work a bit better.

As for future prevention of discolouration, grey or black silicone gives a more pleasing contrast to sanitary ware,

*I* think and I'm hoping will not show the mould as much

John

[Bolted]

Better not to use silicone* at all. Use an MS polymer. 20 odd year expected life, rather than 5. In my limited experience, black moulds don't like it so much (we have a bit in an under-ventilated bathroom where the bath tilts towards the wall).

*not silicon, it's either too cheap or too expensive and not really suited to the task.

[The Medway Handyman]

Tell me about it - I do it all the time.

Shopping list;

1) Snap off knife - basic Stanley knife not as good. 2) Scraper don't buy the SF or TS versions, get the Hamilton & some spare blades 3) Stainless steel scourers like these - Tesco sell them 4) Microfibre cloths - Tesco value ones are brill. 5) White spirit. 6) Small sharp chisel 7) Fugen type tool set 8) Elbow grease. 9) Beer.

Start with the snap off knife - extend about 2" of the blade, hold it flush with the tiles & slice along the silicone vertically.

Scraper next, but don't scrape. Hold flat horizontally against tray & slide along sideways - use it as a knife.

Use scraper against tiles & tray as a scraper to remove any residue.

Vigorously rub with dry microfibre cloth - this will pull out any tiny bits.

Use small chisel to get into corners or behind taps (on a bath).

Wet scourer with white spirit & scrub off any stubborn residue (they don't scratch).

Use white spirit on microfibre cloth to degrease area.

Buy a brand name anti fungal silicone & tool in with Fugen type tool.

Drink beer.

[Lobster]

I'll bet - and if you lived nearer to me I might be giving you a call...

So have you tried and rejected the solvent-based methods?

That looks a key stage - will get myself one of those I think...

Really - even with a s/s scourer on an acrylic shower tray? Doesn't it even take off the gloss finish?

That must raise some eyebrows with your customers...

Many thanks for the tips - I'll press on...

David

[Hugh - Was Invisible]

Too long ago to remember clearly but I think I mechanically removed most of the silicon then applied remover and left quite a long time before removing what I could and repeating. I seem to recall a good outcome but it does take time. The silicone I was removing was only a couple of years old.

Hugh

[The Medway Handyman]

Mainly on time. I can't afford to sit around waiting while it takes effect.

Useful for all sorts of jobs.

Not IME.

I mean you drink the beer :-)

[John Rumm]

A heavy duty snap off blade utility knife is handy - you can extend the blade to a couple of inches and it has enough flex to bend flat against what you are attempting to get the sealant off. Also one of the big sharp 4" scrapers tend to work better than the stanley blade type since you can get a much better grip on them.

[John Rumm]

You want to aim for a bead that is not going to have to stretch more than 10% of its total width in the direction of stretch.

The stretchyness is actually described by the "modulus" of the product. Low modulus products accommodate more movement, but are not as tough and resistant to wear.

What makes a silicone "sanitary" is the inclusion of a fungicide to try and prevent mould growth on areas which are frequently wet.

More to the point, it helps place the silicone in compression when idle, allowing it to relax to its original shape when loaded. This is preferable to having it relaxed when idle and then stretched when loaded.

[Phil L]

It doesn't matter what silicone you use, it will still get mould on it. I've used 'everwhite' - guaranteed to stay white and not allow mould growth.

It was as black as a binbag after six months

[Tim Watts]

Weird - don't know what you guys do... I've had Mapeisil AC white in place for 2 years round the bath and for a shorter length of time, everywhere else and it's holding up well, even though it doesn't always get washed as often as it should.

Don't get black mould on anything...

So perhaps that's a vote for Mapei?

[Peter Johnson]

There was mould around the en suite shower tray when I moved in here in 1997. I cleaned out the old silcon and replaced it with something that I would have got from B&Q. It remained mould-free when the en suite was refitted in 2004; I don't know what was used then. The new installation remains mould-free. I have the window open when the shower is in use and keep the door to the bedroom open otherwise and reckon that that level of ventilation makes the difference.