top coats / skim coat

drummelars · #1 31st May 2006, 10:53 PM

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

echnidna · #2 31st May 2006, 11:43 PM

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

mic-d · #3 1st Jun 2006, 09:32 AM

Quote:

Originally Posted by echnidna

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

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

echnidna · #4 1st Jun 2006, 11:02 AM

Quote:

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

drummelars · #5 1st Jun 2006, 09:33 PM

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

echnidna · #6 1st Jun 2006, 09:55 PM

Quote:

Originally Posted by drummelars

paitning sux after about 2 hours. :mad:

and i have a whole house to do

pay a painter then

mic-d · #7 2nd Jun 2006, 08:28 PM

Quote:

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.

(

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

drummelars · #8 3rd Jun 2006, 08:22 PM

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??

drummelars · #9 3rd Jun 2006, 08:25 PM

i am also using a 1/3 sheet obitol sander

drummelars · #10 3rd Jun 2006, 08:34 PM

i am also using a 1/3 sheet obitol sander

mic-d · #11 4th Jun 2006, 08:28 AM

Quote:

Originally Posted by drummelars

i am also using a 1/3 sheet obitol sander

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

looney · #12 4th Jun 2006, 01:39 PM

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

drummelars · #13 4th Jun 2006, 09:11 PM

nah the house is only 14 years old.

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

drummelars · #14 7th Jun 2006, 10:59 PM

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 ??

drummelars · #15 8th Jun 2006, 06:37 PM

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

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