threads in skim on newly plastered walls after painting twit

[tsmart]

we are experiencing the above after painting newly plastered and skimmed block internal walls which seem and are smooth before applying first coat of emulsion. we have let them dry out and they are very light pink but if you apply white emulsion ridges appear ! this has not happened on stud partitions or ceiling or upstairs only down stairs . it also more apparent on walls with good sunlight exposure. Is it a reaction with the light plaster and paint which is Jewson contract matt emulsion

 

[joe-90]

Did you dilute the first coat by 20%?

If not the new plaster will suck out the water from the paint before it can find a level and it will dry ridged. Better of diluting it and using a roller.


joe

 

[jbonding]

its all the same , youve probably got down lights on the ceiling hiding it and the stud walls havent got light shining on them. sunlight on plaster will show up every thing, like rendering, looks sound then when the light shines on it a bad job is exposed. fixing boards to a stud or ceiling is straight forward but dabbing or floating a block wall is another story and if not done correctly joints will show up and dips and ridges.

 

[Zampa]

The ridges could be trowel marks...or..did you sand the wall before the mist coated it?..if you did the mist coat will have made the fine scratches in the surface swell.

Now its coated try sanding down the ridges and then touch them up with mist coat again.

The walls that are 90 degrees to the light will show things up a lot more.

Tip:- With newly plastered walls, just run a wide bladed scraper over them to remove any snots then mist coat...the mist coat will allow you to rub the walls down (gently) afterwards without scratching em.

 

[tsmart]

we used a jewson contract matt white for new plaster and watered it down and sanded off before . but my wife watered it down 50/50 i did not and did 33.33 % water to 25% mine seems to be ok . her walls are problematic will it right itself as she has sanded down the suspect walls but they look worse . i'm inclined to leave them and put 20% watered matt white on them before painting a pastel colour on them

 

[Zampa]

That should be ok...it doesnt hurt to build up the paint a little to cover the slight surface of the bare plaster.

Be careful with ratios when it comes to watering down paint (or 'pi***ng it out' as we say in the trade...all paints are different in their formulation...in general the better the paint the more water you can add to it.

You can water down dulux crown macpherson by about 505 and it will still perform...leyland and johnstones, not as much..less again for retail paints, even the brand names.