top coats / skim coat

hi guys just wondering with skim coat.

I had sanded my walls back and a skim coat to a few inperfections. I let it dry fo 2 days then sanded it.

I then proceded to wash the walls with suga soap to prep for paint and the skim coat reacted with the water cleaning solution and started to soften up and would SMEAR the skim coat.

Why would it do that i thought it was supposed to set hard and not be affected when cleaning the walls othwewise the paint may peel late on due to not cleaning the walls down.

cheers in advance

Jay

Suigar soap is acidic and plaster is alkaline, so you setup a chemical reaction.

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Originally Posted by echnidna

Suigar soap is acidic and plaster is alkaline, so you setup a chemical reaction.

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Sorry Bob, sugar soap is alkaline. Skim coat does not chemical set, it just dries, so it is still susceptible to water, and water with cleaning thing like sugar soap in it, even more so... After you sand just vacuum or brush the walls clean.

Cheers
Michael

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Originally Posted by mic-d

Sorry Bob, sugar soap is alkaline. Skim coat does not chemical set, it just dries, so it is still susceptible to water, and water with cleaning thing like sugar soap in it, even more so... After you sand just vacuum or brush the walls clean.

Cheers
Michael

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;)

yeah thanks fo that.

bloody skim coat melts like butter when you sand it o even go near it with water.

my walls are still a bit dirty shoud i just lightly dust the skim coated parts down??

I only want to do this job once as paitning sux after about 2 hours. :mad:

and i have a whole house to do:(

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Originally Posted by drummelars

paitning sux after about 2 hours. :mad:

and i have a whole house to do:(

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pay a painter then

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Originally Posted by drummelars

yeah thanks fo that.

bloody skim coat melts like butter when you sand it o even go near it with water.

(

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Are you using a big hand sander with 120 grit? It's good it sands easily, it gets flatter quicker:) You should wash the walls before you skim coat next time.
I find the trick with painting is to prepare properly ie wash and mask everything, then you can have an "out -of-body" experience and mindlessly paint. I hate painting too, BTW.

Cheers
Michael

yeah i think i should have cleaned them before doing the bogging.

the bloddy skim coats melt like butter if water gets near it.

the skim coat is very dusty even after i have sanded it and yes i am using 120 grit aswell.

whats the diffeence bwtween base coat and skim coat??

i am also using a 1/3 sheet obitol sander

i am also using a 1/3 sheet obitol sander

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Originally Posted by drummelars

i am also using a 1/3 sheet obitol sander

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try using a hand sander (looks like a concretors wooden trowel)
Base coat is a chemical setting product used to do the initial fill of joints. It's hard to sand so cannot be used as a top coat. joint compound/skim coat/top coat is designed to be sanded very easily.

CHeers
Michael

if it's old plaster:

you will never get it perfect, if you want it perfect rip it out and use plaster board, but if it's an old house surely this is part of the appeal, well it is to me

i'd use sandpaper just held in the hand, that way you can get the look of it being flat, circular motions get best result

using a flat sanding block will pass some points due to a unlevel surface, use your hand to feel surface and arc light at an angle to check

i fix up many old houses, my clients hire me to get the best job on old plaster before i paint it

i dig out all loose plaster from cracks and where it is bowing out and sounds hollow when you tap it, best to get all loose stuff off, dust or vacume these cracks and holes as the cornice adhesive likes a clean surface to attache to, fill and glue with cornice adhesive, making sure to not get too much proud of surface but also not leaving too much depth to fill as topping does not like to fill more than about 4mm max, takes eons to dry and is not very hard when it does, quick hand sand of cornice adhesive to get any proud bits off as when you sand topping this will make the job hard to get the best end result, then top it, to get perfect job top it twice, if you are really fastidious you can top again after sealing, the sealer will be more reflective and make finish more obvious, sometimes hard to tell as the topping looks flatter than it is

obviously if the areas to be filled are large get a plasterer in, but if it's just cracks and dints most handy souls can do it

i agree, just dust it or vacume and dust, water will activate topping and can spoil it - and where a mask and seal up doors, use a decent sealer/undercoat, cheap stuff is cheap for a reason, it's crap

nah the house is only 14 years old.

its gip rock sheeting. next time i will clean it woks then wipe down befoe piant.

can i use base coat mix to cover up small in perfections likescraped off peeling paint can i do a skim coat of base coat over the top to blend it in ??

here a picture of the stripped back roof that was badly peeling.

how can i blend it in can i use base coat?

http://users.tpg.com.au/jselmes/roof.jpg

i tried to blend it in with top coat but i just wore down with sanding and water killed it

its still not to bad though. im just trying to achieve hiding with the top coat from paint to bare gyprock

Hmmm. I don't Know if you have done the work yet.

But the advice above is right. By the look of the photo you just haven't got it right yet.

Do not use base coat.

Just use top coat, apply it a bit thicker use a 10' joint knife. Then sand as described above with a flat hand sander. Chuck the orbital out for this job.

When sanded just sweep of excess dust with a broom then paint. Don't bother trying to get rid of all the dust. You never will.

If you get any bad spots after painting just skim that local area again. Keep at it it will come up great.

Rod Dyson

Plaster Brokers

yeah mate come up rela nice thanks for the advice.

will try that next time