Urgent, any plasterers need advice

bernlyn

First off whats the diff between the red thistle bonding and the grey thistle bonding is it only colour and also why do fine hairline cracks appear in the bonding when its drying is it because maybe the mix was not wet enough and I did put PVA on the bricks.

Which is the better to use red or grey ??

Many thanks in advance for help.

woolley_2

Sorry I'm not a plasterer by trade but I do my own bonding/lining/skimming when renovating.
Do you mean the actual mix is red - or the products bag colour?
I've never used any other bonding than Thistle - mix is grey and bag colour is purple if memory serves. I nearly always get cracks in it when I use it to patch up areas - usually where it meets the next substrate (ie) when filling chased out channels etc - but as I say I'm not a time served pro!. In saying that it always seems sound and solid though and I can skim over it ok.

Could the red stuff be a Knauf or another gypsum product?

bernlyn

Thistle - mix is grey and bag colour is purple but the bag i bought today is also Thistle - mix is like a redish and bag colour is also purple. another thing this is for the bathroom and i am going to tile it out. should i skim the walls or is it ok the tile over the bonding

nelly_2

I'm a plasterer and even went to college

There is no difference at all, its just the gypsum is mined from two different parts of the country.

PVA- Although its a bit late now when pva-ing you need to give it a coat, let it set for an hour-ish, then give it another coat. The first coat is adequate for adhearing purposes but the second coat stops the bricks absorbing the water out of the plaster causing cracks. If the cracks are bad pva it (once should do if its still wet) and then just do a tight/thin coat over the lot again.

Tileing on bonding is fine I never bother skimming it.

nelly_2

woolley wrote:

Sorry I'm not a plasterer by trade but I do my own bonding/lining/skimming when renovating.
Do you mean the actual mix is red - or the products bag colour?
I've never used any other bonding than Thistle - mix is grey and bag colour is purple if memory serves. I nearly always get cracks in it when I use it to patch up areas - usually where it meets the next substrate (ie) when filling chased out channels etc - but as I say I'm not a time served pro!. In saying that it always seems sound and solid though and I can skim over it ok.

Could the red stuff be a Knauf or another gypsum product?

Same again for your cracks, the walls pull the water out that fast (mixed plaster is about 40% water) that it literally shrinks, thats what causes the cracks. Flicking pva in first prevents this, although having a load of wet pva running down a chase into a plug socket produces some interesting results

Nile

Thanks for your expert opinion nelly.:T

tomstickland

A guy at work who's got C&G quals in many building trades including plastering told me today "I can teach you most of what you need to know about plastering in two hours". That surprised me because I always though of it as a Black art.

nelly_2

tomstickland wrote:

A guy at work who's got C&G quals in many building trades including plastering told me today "I can teach you most of what you need to know about plastering in two hours". That surprised me because I always though of it as a Black art.

Its true its like screwing the ball back in snooker takes 5 seconds to explain how. Thats it theory over.

Knowing how hard to hit it to get the white ball to exactly where you want it canot be taught you have to practice over and over again.

woolley_2

nelly wrote:

Same again for your cracks, the walls pull the water out that fast (mixed plaster is about 40% water) that it literally shrinks, thats what causes the cracks. Flicking pva in first prevents this, although having a load of wet pva running down a chase into a plug socket produces some interesting results

Ha ha Yeah - Thanks Nelly - plug sockets/lights switches or anything that has to be gotten around always poses even more fun later on for us self taught novices when it comes to skimming. Any area I can't get the trowel in properly makes me (a slow plasterer) that much slower!