pva vs bondit/wba/gypbond etc

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bigsegs

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k, dont think weve done this as a discussion...couldnt be arsed with a 'pole' so...
whats everybodys views on pva vs bondit etc...my understanding is bondit and the like kill all suction but give you a sandy 'key' to hold the plaster on...
i prefer suction to hold my plaster on, i reckon gypbond is a bit like havin sand in gloss paint, though ive never used it...who wants to change my mind? I do realise though that 'thistle bond it is the only blah recommended by british gypsum etc...' according to their site...but how long has it been invented, and what did we all do beforehand??
 
i started using wickes bondit after reading bout it on this site, think its the mutts nuts but have gone back to pva, don't have to wait so long before you can skim it and its cheaper. i think i mentioned in another thread that squeak when i walk! ;)
 
what do you use for overskims pug? multi or board? cos i think it might be relevant..
 
i use use pva on walls and wba agent on all ceilings, what ever the surface, one way to look at it is that plaster sticks to pva or wba or bont it, so they all work. accept that one job you done Bigsegs, i just prefer to use wba on ceilings especially when over artex because of the key.
 
now then...this is the thing...my understanding of all things 'wet trowel' i.e. plastering/brickwork/rendering is that what happens is the background draws water into it via capillary action, bringing with it some of the mix, therby forming the key, bit like tiny little needles...and plaster/render dries from the back. ive seen people pointlessly placing heaters in front of render in winter so they can float up quicker...doesnt work though does it?
that said, a hot room will dry skim quicker...which brings me to the only other problem ive had with overskim which was the bloody stuff went off like lightning, both coats and when it dried i had tiny little hairline cracks just here and there...
what i mean is...when i pva a surface, what im under the impression im doing is not killing the suction, but bringing it down to manageable levels...if youve ever had a wall that had 'some' gloss paint in places youll know what i mean, when i overskim someones bad plasterwork i give it loads of pva but it still doesnt kill it all...
 
what do you use for overskimming christ? multi or board?...think gary mentioned multi likes suction, boardy doesnt need it...or can get on with less...
 
multi on everything bigsegs, and always 2 coats of pva. now don't quote me, but i believe cement molecules, when wet, lexpand like sea anemones and as they dry the spikes grab hold of whatever they can and therefore, "stick", is this relevent to this thread? a bit p*****d! ;D
 
im the same, just multi...
what im trying to explore though..is why
i remember gary mentioning the multi/board difference from way back when it was carlite
makes sense...bit like the bonding vs hardwall, i.e. bonding doesnt like too much suction but will stick to anything...not quite sure why though, im no chemist...
what you say bout cement expanding makes sense though,seein as cement based stuff shrinks on drying/curing...
the multi on wba thing though...does it grin at you for ages then go off all at once??
 
not that i noticed, i like to leave it till quite late before i trowel up anyway tho.
 
ok when plastering a big ceiling 25m2 when using pva when you've started it was tacky by the time you've finshed the pva had gone off and lost its key, thats why i use wba. maybe im slow
 
you ever had it do that though...had it a couple of times when i wasnt too sure of the background and pva'd it anyway...its done its 'sliding down the wall trick' so i left it, but it caught me out, wasnt for lack of testin it though...just felt really gritty all at once, put it down to oversealing...
reason im not to keen on board is that i can put up to about 30m on on my own, i flatten at plasticene stage, then top it immediately..boardy seems to go a bit quicker on first coat then gives the time back to you on 2nd..consequently i find im more in control with multi and get a better finish without gettin trowelarm...
goin off topic, anyone know whether bondit actually DOES kill all suction or is it some sort of microporous coating that gives a perfect amount of suction?
 
i've always assumed ( and we all know about assumption being the mother of all wassanames) that if the pva has gone off, the water in the gear would retackify it. i've not had a ceiling fall on me yet, (famous last words!)
 
ok i left my roller out with pva on it when it went hard i washed it out, my roller went hard with wba on it and it still was rock hard when i tried to wash it out, to me that shows water wasnt gona break the wba down stoping all suction, but i might just be pissed
 
nah christ mate 25m is a big ceiling on yer own, i feel it, i do a max 30 on walls..
so...are we sayin then, that pva supplies a key...i tend not to notice too much difference if it HAS dried, in fact ive skimmed over well dried silk paint without pva and its gone lovely...
they go on about tricky timing on gypsum site..maybe this is why yes?
im a bit p"""d myself btw pug :)
in other words my theory bout needin suction is bollox? could be right including all the info...
 
k, just read yer last 2 post lads, (makes 3 of us btw) ;D
so, pva lives up, suction is still a possibility, but wba kills it all but gives you a grit..
does it make a difference???
and what is the difference? either of you tried boardy over wba?
 
i know nothing about plastering ive only been doing it about 10 minutes, i only do what i think is right, and what ive learnt from you, when i first joined the site
 
never used boardy ever. as for suction (pva) over key (wba) i don't know! its an enigma mixed with a conundrum wrapped in a mystery! as long as the plaster sticks i'm happy :)
 
all i can say is that when doing a big ceiling 30m2 use wba but dont roll it out to thin because it will go of quick. if you roll it on thick you 'll have loads of time to trowel up
 
ah come on lads, im not grillin anyone, im in the same boat just cos ive been on the trowel for a few years doesnt mean i know everthing!! thing is im a general sort of bloke, i can turn my hand to most things, its just that these days im concentrating on plastering only..
im only trying to understand the reasons why we do what we do and in what circumstances...i too am more than happy if i get a good finish, it doesnt come off and i get no call backs...which seems to be the case...
BUT..like anything else, and trust me on this, the more you understand about the products you work with day in day out, the easier your job becomes = more money for less work..
im just trying to get my head round how plaster works in the microscopic sense...
e.g..
skimming over hardwall - let it firm up, dont pva it straight on works a treat...
anything you allow to 'cure' needs the suction bringing down to manageable levels
killin all suction, to me anyway, is a bit like skimmin over gloss paint, a f;;;kin nightmare...at least with multi..
so..you get a sandy key with wba, but would it still not behave in the way skimmin over gloss paint behaves? just that it wont fall off but will still be awkward?
i tend to find that just the right amount of suction using multi gives me all the time in the world, no effort, easy money...any problems and i feel ive f''ked up and underquoted a job...but then, thats down to my lack of knowledge yes?
thanks for your input though lads, much appreciated :cool:
 
no shame in it our kid! i'm on vodka an coke meslf, off to bed shortly though, work in morning :(
 
LOL im on the red too, got an echo falls californian...thing is im mixin it with coke to make 'poor mans sangria'..goes a lot further and the bubbles get you p'''d quicker!!
 
yeah more suction or less suction doesnt mean its gona stick to anything, if you paint gloss on gloss with out sanding it, it'll flack off. if you sand it first making a key for gloss it'll stick to the key, plus they both dry at the same time
 
not at all bigsegs, i agree with you 100% i think that sometimes, like you say you are with multi, although there may be other products on the market, if you're comfortable with the materials you know, using something new means starting having to relearn stuff, and perhaps screwing up jobs you wouldn't normally struggle with... or maybe i'm stuck in my ways!
 
hey big. just try wba for your self, its one lol. i think plastering taking over my life, ive bought 4 differnt marshalltown trowel and i still want to buy more. :D :eek:
 
yes christ mate, i understand gloss paint needing a key, but its oil based...plaster isnt, bonding/tile adhesive is a different story...something in them makes em stick to anything...key or no key...long as there ISNT too much suction..
funny game this y'know, people say it aint rocket science, but its a science nonetheless...
prolly have to give it a shot on a small ceiling and report back to plastering hq :D
as for the trowels..
i ran on two ragni 14 inchers for years, lost em...
now im on a shitty little ragni which i got from screwfix where they changed the handle to look like a marshaltown,great trowl but the handles loose...big mistake..
marshaltown stainless..not keen
bought a tyzak 'ready to go' stainless, prefer the old ragni, bust handle included
bought a marshaltown wotsit midget trowel, gets me out of all kinds of shite...
lookin to buy a tyzak worn in STEEL..i just dont seem to get on with stainless...leaves a fur on the final trowel...
 
i'm still using the worn in marsalltown stainless i started with so i don't know any different, but a lot of fellas swear by wooden handles to stop cramp an stiffness, any truth in this?
 
right then, nice one christy..
so...no key, no stick, prolly obvious
but...anyone agree that pva supplies key via limited suction but suction nonetheless...
wba kills suction but provides a key via grit....

so...havin not tried the stuff....does it make much difference to the way your layin on/trowelin up/timings etc...
 
pug...i tried a worn in marshaltown after bein on a plastic handled ragni for a few years and it killed my forearm, i gave it to the apprentice and he had no problems with it...i reckon choice of trowel is purely individual, bit like your fave pair of jeans...
 
i dont no big mate, if it works for you then its right, i use wba on ceilings and pva on walls because it works for me, ive tried most trowels on the market cost me a fortune, like mt the most so thats why i use them, dont rule anything out till you've tried it
 
nah mate im not, thats why i started this thread..the stuff is ridiculously expensive though for what it is..im seroiusly thinkin of givin it a go..gotta move with the times and all that..
 
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