Gib compound

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tims

118 posts

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#260237 17-Nov-2019 09:13

I've finally finished stripping wall paper off my walls and am using Gib trade multi air drying compound I bought a while back to plaster over the old plaster (cement based) walls.
I've done most of it but have noticed some grey/black smears while applying the compound and have finally realised that the compound has spots of mould all through it. It appears to be setting to a hard normal finish but now I'm concerned about whether the mould is a health concern especially when I'm sanding prior to painting.
Any thoughts if this is a valid concern or would this be just harmless mould?

ps just looked at the boxes the compound is in and the best before date is a couple of years ago - didn't realise it had an unopened shelf life.

tdgeek

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#2354993 17-Nov-2019 10:07

Id spray all the walls with 100% white vinegar, that will kill the mould, better than bleach. Maybe do that twice. use a garden sprayer to make it quicker. Then sand. This might be a good option, while its key to remove/kill the mould, this might be a nice backstop

https://www.bunnings.co.nz/zinsser-1l-white-mould-stop-primer_p01570019

Oncop53

273 posts

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#2355277 17-Nov-2019 20:23

I am a professional mycologist and had the same thing happen to me, so don't feel bad!

You breathe in many thousands of mould spores every minute, and of course eat blue cheese etc. so mould spores are not intrinsically bad. In terms of sanding I'd be more worried about the silicates in the sanding dust than the spores, you do wear a mask right?

The other concern is mould growing though to the surface, but you are painting rather than papering, so they wont get any food or moisture and soon die. If you are really worried about the colour showing through a light coloured paint, use a solvent based sealer like Resene Sureseal.

Fred99

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#2355614 18-Nov-2019 11:47

Oncop53:

more worried about the silicates in the sanding dust

I'd hope that any silicates in something like that would be amorphous, synthetic precipitated silica etc, not crystalline. So an unpleasant nuisance dust to be avoided - but not a risk for silicosis.

When I've bought pails of compounds like those, they're often mouldy when past expiry date unopened, and once opened but not fully used they grow mould quite fast. I guess there's enough organic matter in the plaster - cellulose fibre etc - to feed the fungus. Maybe there's no effective biocide added - as in that case you'd possibly end up inhaling some of it as dust.

I used to be involved in supplying industrial biocides. Was like a game of "whack a mole".