Mastic not setting

[Jimk]

Ime they usually go solid in the tube, rather than non-setting, but spose it depends on the chemistry of each sort...

[Jimk]

Been to Specsavers ;-)

[Jimk]

9th line down?

[Jimk]

Silicone = rubber

[Jimk]

Kin ell I hope you didn't pay 15 quid a tube for it!

[Lee Nowell]

Hi All

On Saturday I did some mastic around an outdoor worktop. Oddly, the mastic has still not fully set. Given the temperature I would have thought it would have done more quickly rather than less. Any ideas?

Thanks

Lee.

[charles]

Surely mastic never sets, but remains flexible

[Richard]

Stupid question maybe, but is it the right mastic and not a non setting mastic?

[Lee Nowell]

Ah I didn't know there was such a thing as a non-setting mastic. This is what I have

It says it supports high movement and the instructions does not give a curing tine.

[harry]

Mastic is not intended to set. It's supposed to remain flexible. Mastic= Plastic

[Richard]

Erm, it does give a curing time in the specs from your link:

Colour Grey Application Bonding, Exterior, Sealing Package Size 310 ml Package Type Cartridge Minimum Operating Temperature -50°C Maximum Operating Temperature +120°C Food Processing Safe No Physical Properties Low Modulus, Neutral Cure, Waterproof Cure Time 1 (6 mm) day Product Form Paste Operating Temperature Range -50 ? +120 °C

[Richard]

You're on the ball today.

[Lee Nowell]

Thanks all. No didn't pay that for it. Was just the easiest link I found when googling it :). Can't recall where I bought it TBH.

By curing / setting I mean that it goes into a rubber like product which holds its shape but distorts/ flexs as you push/ move it. Like bathroom silicone. This is still tacky to the touch and if you run your finger over it it will come off similar to when you first put it on. Having said that it is a bit more rigid / thicker than when it came out of the tube.

Thought it might have gone off maybe but it was an unopened tube.

[Robin]

How old an unopened tube? I ask as I used some a few years back that was well past its best before date. It took a little time to set properly: over 6 months.

[Richard]

That's why they have "use by dates".

[Andrew]

I had some neutral-cure silicone stuff and when I used the remains of one tube, about 8 months later, it took about a week to skin over and never really set properly.

[Andrew]

I have noticed the same on neutral-cure 'mastic', but only when using a tube that was part used and stored (indoors) for a a few months. It just seemed to take a long, long time to skin over and 'set'.

[Lee Nowell]

To be honest I can't recall when I bought it. I would guess it is several months. Just checked the tube and no use by or manufactured date so hard to know whether that is the issue.

[alan_m]

Skin formation takes approximately 10-20 minutes dependent on bead width, temperature and humidity. EVO-STIK Building Silicone Sealant dries through at a rate of 2-3mm per 24 hour

Both at 23C+ and 55% relative humidity

[alan_m]

In the sun it may feel hot but the average temperature over 24 hours in the south of the UK is in the low teens.