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Painting fresh plaster/renderlite... black & red paint..??

Discussion in 'Decorating and Painting' started by Soggy Bottom, 11 Jun 2019.

  1. Soggy Bottom

    Soggy Bottom

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    Few questions here.

    1) How soon after a fresh plaster job can you paint it?
    The last time i did it i wasn't in a rush so i let it totally dry out so everything was light pink. Is it possible to do it before that or is that the earliest?

    2) Can someone refresh me on how you prep fresh plaster for painting?
    I did this years ago but i'm not 100% sure. I bought some Dulux Supermatt. I think i went 50/50 with it water:paint. Then i did something like a 70:30 or 80:20 Paint:water. I can't remember now. I'd then apply the colour.

    3) The above is for painting a freshly plastered (Multifinish) wall. How about for painting a wall that's had Sovereign Renderlite applied, which is a lime based render & is quite rough to the touch.
    Same process?

    4) The Renderlite wall will end up being painted black. The plastered (multifinish) wall will end up being painted red.
    The Dulux Supermatt i have is white.
    How are you supposed to prime the walls for red & black paint?

    I remember when i painted the wall red the first time round and it was an absolute nightmare. I had to do something like 6-8 coats, likely due to the white undercoat.

    Is there a way round this / how would you work it? Would you apply Dulux Supermatt as described and then go buy some cheap grey (or some other colour?) paint to give it a decent dark coating before then hitting with the black & red where appropriate?
     
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  3. Soggy Bottom

    Soggy Bottom

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    At the very least then would the better bet be to buy in a red colour https://www.diy.com/departments/dulux-easycare-pepper-red-matt-emulsion-paint-2-5l/1643151_BQ.prd (or perhaps something cheap & cheerful although same colour as top coat - before putting a decent paint on top) and then use this as a mist coat going 50:50 before putting your red top coat on?

    I bought more than one tin last time round & have an unopened tin. Problem is it's been discontinued so i don't really want to use that one as the mist coat & not have enough left for the top coat. Equally i don't want to paint the sides of the chimney breast if i don't have to.
     
  4. opps

    opps

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    I would just buy the black and red emulsions without using a white base coat.

    I'd get the colours mixed in Dulux Trade matt and mix the first coat 1 part water to 5 parts paint (17% to 83%) as per the instructions. 1 thinned and two full coats should suffice.

    I have never understood why people use a 50/50 mix. It is messy, requires more coats and does little to reduce the level of suction.

    BTW if the tin doesn't mention the word "Trade" it is the retail (rubbish) version of Dulux.

    Supermat can be problematic as a base coat. As a paint with a low acrylic content, it is supposed to be used on new plaster that is not perfectly dry. It is not designed to be used as a "primer" under regular emulsion.

    With regards to when the new plaster can be painted, once the colour is a uniform light pink, it should be ok to proceed. Leaving windows open will help the plaster to dry.
     
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  5. Soggy Bottom

    Soggy Bottom

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    Thanks.

    I actually have the tin ready to go. I bought it probably 2016. It's unopened (i actually have 1 opened tin but wonder what condition that's now in & 1 unopened tin).
    Thing is you can no longer get it (Dulux Endurance+ Salsa Red) so i don't particularly want to use it up watering it down and then applying top coats only to find that by the time i've emptied the tin the coverage isn't quite right and i no longer have enough paint left.

    Which makes me ask - what about buying in a cheap tin of red paint (say Wilko's own brand, B&Q own brand etc, so long as it's matt red of some description), using that cheap tin of red to do the mist and then going with the Dulux paint as the top coat?


    Or is that a bad idea for some reason that an experienced guy will know that i can't think of?


    As for why going with a 50:50 ... that was what i read to do at the time. I remember searching for answers & as ever i never stop at the first answer i get. 50:50 was coming up frequently so that's what i went with. It made sense to my beginner brain because i thought it's fairly watery so should suck in very well and allow for the plaster to be sealed ready for the top coat. Like you said though, it wasn't great to work with at that ratio.
     
  6. opps

    opps

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    Salsa red is still a Dulux colour.

    You can get it mixed in Dulux Trade Diamond matt- that's the trade version of Endurance +

    eg https://www.brewers.co.uk/product/AE0122520J/Salsa+Red

    Any decent decorators' merchant that sells Dulux Trade should be able to mix it for you.

    I'd recommend using your old stuff as the base coat and then the trade stuff over the top.

    The trade paint is much thicker. The first coat will seem overly thick but once it has dried the second coat will flow nicely. That is the result of the first coat sucking in quite quickly (even when applied over several coats of existing standard emulsion). The first coat of full fat Diamond matt will make the walls far less permeable/porous.

    If you don't want the added expense of buying a tin of Diamond matt, why not get a cheap paint of something like Leyland matt emulsion mixed, ask the shop to mix it to the nearest match in the leyland colour range.

    Reds can be a pig to cover, even when using red to cover them. Yellows can be even worse. Dulux use the euphemism "special process" colour, which is shorthand for having to apply loads of coats (needless to say, they don't warn you when you ask for the paint to be mixed).

    Apropos the 50/50 mix- I am the cleanest decorator that I know (no, seriously, so much so that no one looking at my clothes believes me when I tell them what I do for a living). I would struggle to apply paint that thin without making a mess. One thins paint, not so that it soaks into the plaster per se, but rather so that the plaster doesn't suck too much water out of the paint as it is curing. Waterbased paints coalesce as they cure- the water evaporates off and the molecules "shrink" back to form a thin film. If to much of the water is soaked into the plaster, the coalescence process is compromised. If the paint is overly thinned, the coalescence process may be compromised, and the next full fat coat may be compromised.

    In practice, no, I have never seen emulsion fail because the first coat was 50/50, but... typically an extra coat is required. Labour costs are far higher than material costs when painting emulsion.
     
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  7. Soggy Bottom

    Soggy Bottom

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    Thanks very much for the info.

    When i did the walls first/last time round i actually went with both sets of advice that i was finding online - i initially went with a 50:50 mix and then went with either a 70:30 or 80:20, i can't remember now. Then was going with the top coat.
    Sure it may have ended up taking more time but i had time and did this as a bit of a 'play safe'.

    Unfortunately my better half has arranged to have the fire and new hearth to be fitted midweek, so i don't have time to get this paint mixed up (they're not open Sunday's). I'll have to see if what i've got will cover it. I think the tin said 35m2 and i'm only doing the face of the chimney breast this time round as it's been overskimmed, so i should have enough.
     
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