Annoying little lumps...

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RMK

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Hi everyone!

I'm new to the forum, and have had a quick look through all the topics raised, and found all the responses in-depth and very helpful - Some guys really know their stuff!! :)

I have a problem which comes with around 5% of the work i do... and i don't know why it happens! Really small lumps in my walls (imagine like a rash on your skin) come out of nowhere in patches, and they won't trowel out! The only way to get rid of them is to wait until the next day and polish them off with water.

I read a similar topic on here where small bubbles occured when skimming over 'thistle bond-it' (i too have had that happen), and the reason for those being was because of the aggregate element in the product, and it was advised a thicker base-coat should be applied.

My problem happens when skimming plasterboard...? The only thing i can think is that the plasterboard was contaminated, but surely that can't be the problem every time?

Any suggestions...??
 
Hi and welcome to the forum,

Do you use water when you trowel up? i.e. flick lots of water on the wall with a wetbrush?
the reason i ask is it normally happens over bonding or hardwall not bond-it and other areas of differing suction..

bondit or wba doesnt give me problems, but i use board finish not multi on it..

i think the only time ive seen it happen on plasterboard is when some 'other' has put em up back to front and ive given em a lick of pva...

those lumps will trowel out when it starts to go brown, no need to wait until the next day..
 
I am trying to limit the amount of water i use to get a uniform colour to the finish, but have been using clean water through a sprayer where needed.

It's wierd... as i say i get a spot on finish 95% of the time, and i guess these lumps are negligeable as you wouldn't really see them with a coat of roller-applied emulsion, but i know they're there and you can see them if, for example... you put your eye to a wall which gets a lot of natural light.

The lumps won't trowel out, or polish out when the rest of the wall is ready at each stage... and considering this occurs when plastering on the board... it's confusing.
Could it be from putting too much plaster on do you think??
Or potentially over-working the plaster??

ps-Board finish is the mutts wotsits ;)
 
it could quite well be that your putting it on too thick, in the absence of excessive water for flattening the first coat id say this is more likely than over working, though over working could contribute
if you put plaster on too thick it generally gets a few ripples in it, especially multi as it will have a tendency to go off all at once, board finish less so, but if you end up trapping too much water in it then its gotta go somewhere and the little pimples are the result..
how long have you been skimming mate? reason i ask is some of the lads ive had working for me who ive taught at first try and mix up thin to give them more time, then i explain it'll go off quicker cos its on too thin so they compensate by mixing up normally and laying it on silly thick which ends up 3mm proud of the door liners!
again, i cant say i get it on board but it happens occasionally on the overskims round beads especailly where its on thick and i may have overdone the pva..
end of the day, i wouldnt worry too much, they come out in the end and although theyre a pain in the arse we all get em from time to time.. nobody's perfect ;)
 
Have been skimming for 3 years now, but have only got my finish up to a standard i am consistantly happy with over the last 6 months.

Trapping too much water in the wall kind of makes sense as the most recent example of this 'lumpiness' happened when i was skimming a bedroom wall, which link to the stair well and to downstairs. Went to do the lot in one go, so did use a slightly wetter mix than usual, but also built up in areas where the boards were slightly out (cos i hadn't done the dot & dabbing). I guess that's both examples of what not to do really...

Why do you say NOT to use a wetter mix then?? I find it is the only way i can get around larger areas usually... and it usually works fine?
 
plaster has a chemical set time, its designed with retarder ratios to go on at around 2-3mm thickness and gives about 1.5 hours set time per coat...
if you mix up real wet, its thin, and if its thin it'll come off your trowel thin. Try plastering an artex ceiling with p'ss wet plaster, it'll take 3 coats.
if you mix up normally and your suction control is correct you should end up with the perfect finish if you lay on as much as you can handle.
i do make my topping slightly wetter if the first coats gone on nice but if not ill lay on same again, sometimes its the only way to get round other problems such as dips in the background or heavyish artex..
overskims are different cos you can pretty much kill 90% of the suction and lay on a bit thinner, the suction wont have the same effect and youll find you can lay more on but its still a timing thing again, top it too soon and youre trowelling the whole lot up together...
it also depends on what you call 'thin' if your used to knocking up like cream cheese as a normal mix and have arms like arnie then a thin mix to you would be about normal for me.. :D
 
I think the blemishes your on about are caused by water being trapped behnd the skimming. This forms the blemish but when the water dries out the blemish can be trowelled out. Sounds like what Chris said and that you might be putting your 1st coat on too thick mate.
 
ok guys.
thanks a lot for the advice.

will keep the mix consistent and hope it solves the problem.

chris w... i've always wondered... i always aim to get my total thickness over the surface (both coats) to 2-3mm... but are you saying that each coat should be between 2-3mm... therefore total thickness could be between 4 and even 6?? surely not??? have i read this wrong??

this site is awesome btw!!! i'm trying to take advice from anyone at all on a day to day basis at work, but this just adds to it all. :)

ps... very whitty with the lumps refs. ha
 
total around 2-3 mm mate, ideally, on board, flat off the edge of the bead and door liners etc..
overskim can sometimes go on a bit thicker obviously..
 
I'm sure its just a thickness and a timing thing , laying on to thick and second coating to quick , over troweling will not help just get your timing right and things should become easier for you
 
I get these dimples too sometimes, normally we mix the first coat so its like chocolate mousse, not too thick but not too runny, if its too runny it goes everywhere and you cant get enough on the wall. We normally do 30-40 metre sets so if its a thin coat it will go off quicker and its a nightmare to trowel up. Second coat is a wee bit thiner but thats when the bubbles appear. Sometimes they won't polish out and its not great. We don't play with them as the more they are troweled the worse they get. Its a pain in the Ar@~
 
Peg... That is exactly what i have been experiencing! So you recon it's down to not getting enough on on the first coat then mate?
 
If you're two-coating, are you laying down the first coat and letting it pull in before applying your second?
If not, it's like one-coating which 'will' bubble especially if you're over-working it.
'Less is Best' when it comes to finishing off :-)

Pete.
 
Don't know whats causing it, i normally lay on a lot with both coats. First coat gets one flatten then it gets topped. Don't play with it too much and its normally had a chance to pull in by the time the second coat is on. We normally do about 30 - 40 metre sets so it takes at least a half hour to get it on and flatten it. Its weird!
 
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