Blebs

MakeItSmooth

Well-Known Member
I’m not 100% sure that they have the data in a technical format but I will ask.

I will ask the scientists but be warned, I might not be able to spell some of the words they use, never mind understand them.


Made me chuckle!


Sorry, when I said 'technically', I didn't mean to the extent of scientific formulas and test tubes :ROFLMAO:

I just meant I would like to know in plain english specifically WHAT is actually happening that gives rise to blebs - what is the mechanism, rather than anecdotal explanations of 'tends to happen when too wet or applied too thick' etc.

With regards to your question on blebs on your bonding, how long are you leaving it before you skim it?

Varies. Sometimes left overnight before skimming, sometimes just a couple of hours, sometimes half a day. Of course it doesn't bleb everytime, but if I had a better understanding of exactly what causes blebs, then it'd be easier to consistently avoid them, rather than getting caught out now & then. I bet most spreads have had to deal with them, occasionally, and no one likes having extra hassle in their day.


The vermiculite in Bonding would not be effected by the application of a finishing coat once it has set.

No, I meant the other way around. Vermiculite is randomly dispersed throughout the applied area of bonding on a wall, some chunks of vermiculite will lie deeper than other chunks. The shallower chunks will have less gypsum (from the bonding coat) between them and the next coat of skim. Is it possible that this could make those tiny areas less absorbent - i.e. pull less moisture out of the subsequent skim layer?

I'm only guessing, and I could be a thousand miles out.

All I'm asking is for a better understanding of what actually causes blebs. Maybe the BG boffins aren't sure, or maybe they do have a useful answer. I can only ask
Shrug TPF.gif


In the meantime, I will bear in mind what you've mentioned about wet substrate and thickness (y)
 

Brimstone

Well-Known Member
I thinmk Make it Smooth is right on the money - Thank you! Web search;-

Perlite and vermiculite are lightweight, making them valuable for this application. They each also have their own unique properties that improve gypsum plaster.
Perlite is one of nature’s most versatile and efficient minerals, formed by volcanic glass. It has high permeability and low water retention. Perlite has a fissured and cratered surface which does hold some water on the outside. But it holds on to little water, mainly allowing it to slide off. Perlite has no cation exchange capacity.- ?
Vermiculite is a hydrated magnesium aluminum sheet silicate mineral.
Vermiculite, on the other hand, will hold and store water within its layers. It works a little like a sponge and will absorb water and expand in size. It will then slowly release the water it has absorbed over time.
Vermiculite is highly effective in cation exchange capacity. -? In Cation Wha?

Cation exchange is a reversible process in which the cations are exchanged or interchanged between the solid and liquid phases or between the solid and solid phases when they come in close contact.

AHa! So if not fully dried out, when you squeeze it with another pass/coat, solid changes back to liquid, and it blebs! Right?
 

Brimstone

Well-Known Member
Cations are apparently bits of positive electrickery (ions), like static makes it stick - so a pass over pushes them together and changes the static - and maybe that's what makes the difference between using a steel or plastic spat??
 

Monkey Boy

Well-Known Member
Cations are apparently bits of positive electrickery (ions), like static makes it stick - so a pass over pushes them together and changes the static - and maybe that's what makes the difference between using a steel or plastic spat??
Yeah speedskim plastic blade let pick up big time one trowel done blebless?
 

The Apprentice

Well-Known Member
I’ve spoken to the scientist regarding blebs. He tells me it’s not a chemical reaction that causes blebs, if it was you wouldn’t be able to trowel them out. His belief is that they are caused by excessive moisture, be that caused due to the substrate or excessive depth of skimming. The moisture accumulates in areas and as it gets absorbed that’s when they can be trowelled in.
 

theshed

Well-Known Member
Is blebs a northern thing like handboard instead of a hawk. Everyone I've worked with calls them blisters.
 

spread95

Well-Known Member
I’ve spoken to the scientist regarding blebs. He tells me it’s not a chemical reaction that causes blebs, if it was you wouldn’t be able to trowel them out. His belief is that they are caused by excessive moisture, be that caused due to the substrate or excessive depth of skimming. The moisture accumulates in areas and as it gets absorbed that’s when they can be trowelled in.
What a load of tosh bg at its best!! We only make it, if theres any problems it the spreads fault!!
 

MakeItSmooth

Well-Known Member
I’ve spoken to the scientist regarding blebs. He tells me it’s not a chemical reaction that causes blebs, if it was you wouldn’t be able to trowel them out. His belief is that they are caused by excessive moisture, be that caused due to the substrate or excessive depth of skimming. The moisture accumulates in areas and as it gets absorbed that’s when they can be trowelled in.

So, the BG explanation is that it's definitely, positively, got absolutely nothing at all to do with BG bonding?

Funny that when blebs happen, bonding quite often tends to be on the wall. Admittedly, that doesn't prove causality, but it's a heck of a coincidence.

Just to clarify, I never suggested a chemical reaction. I was thinking about possible uneven moisture absorption, on account of randomly distributed particles of vermiculite varying the thickness of the bonding gypsum lying underneath the skim layer.
 
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ChrispyUK

Well-Known Member
So, the BG explanation is that it's definitely, positively, got absolutely nothing at all to do with BG bonding?

Funny that when blebs happen, bonding quite often tends to be on the wall. Admittedly, that doesn't prove causality, but it's a heck of a coincidence.

Just to clarify, I never suggested a chemical reaction. I was thinking about possible uneven moisture absorption, on account of randomly distributed particles of vermiculite varying the thickness of the bonding gypsum lying underneath the skim layer.

I’ve had it on hardwall too.
 

Monkey Boy

Well-Known Member
I thinmk Make it Smooth is right on the money - Thank you! Web search;-

Perlite and vermiculite are lightweight, making them valuable for this application. They each also have their own unique properties that improve gypsum plaster.
Perlite is one of nature’s most versatile and efficient minerals, formed by volcanic glass. It has high permeability and low water retention. Perlite has a fissured and cratered surface which does hold some water on the outside. But it holds on to little water, mainly allowing it to slide off. Perlite has no cation exchange capacity.- ?
Vermiculite is a hydrated magnesium aluminum sheet silicate mineral.
Vermiculite, on the other hand, will hold and store water within its layers. It works a little like a sponge and will absorb water and expand in size. It will then slowly release the water it has absorbed over time.
Vermiculite is highly effective in cation exchange capacity. -? In Cation Wha?

Cation exchange is a reversible process in which the cations are exchanged or interchanged between the solid and liquid phases or between the solid and solid phases when they come in close contact.

AHa! So if not fully dried out, when you squeeze it with another pass/coat, solid changes back to liquid, and it blebs! Right?
Vermiculite I think used by gardeners to assist with drainage in soil
Misnomer really “drainage” rather should be “spongage”
 

Brimstone

Well-Known Member
It's great for growing seedlings in, no soil, they germinate and grow enough in just the vermiculite - then to transplant you just pull them and they come out easy with no root soil.

chinese takeaway box, couple of holes, fill with vermiculite, bit of water, add seeds, done. Plastic bag over it with a couple of sticks if you want.
 

Brimstone

Well-Known Member
I’ve spoken to the scientist regarding blebs. He tells me it’s not a chemical reaction that causes blebs, if it was you wouldn’t be able to trowel them out. His belief is that they are caused by excessive moisture, be that caused due to the substrate or excessive depth of skimming. The moisture accumulates in areas and as it gets absorbed that’s when they can be trowelled in.
sorry, did'nt see your reply, ignore my later comment.
 

essexandy

The Lake Governor
I’ve spoken to the scientist regarding blebs. He tells me it’s not a chemical reaction that causes blebs, if it was you wouldn’t be able to trowel them out. His belief is that they are caused by excessive moisture, be that caused due to the substrate or excessive depth of skimming. The moisture accumulates in areas and as it gets absorbed that’s when they can be trowelled in.
Gary with all due respect, your scientist is a useless, know nothing c**t. Has he ever even seen Bonding in use or looked into this issue? Blebs are trapped air not moisture.
Sack him and give his wages to a childrens charity.
 

ChrispyUK

Well-Known Member
How do you?

Depends on the construction of the property and what’s already on. If I overboard a ceiling and it’s a bit wavy then I’ll usually take a bit of time to straighten out the ceiling lines. Could be with skim as I’m doing it, or bonding before.
 

essexandy

The Lake Governor
Depends on the construction of the property and what’s already on. If I overboard a ceiling and it’s a bit wavy then I’ll usually take a bit of time to straighten out the ceiling lines. Could be with skim as I’m doing it, or bonding before.
I don't think you noticed that I altered your quote lol
 

elvis90

New Member
Doing some subby work for a housing association currently kitchens and bathroom refits. Using a bag of bonding per kitchen roughly and not had one single issue with blistering over the backing coat. Knocking up the bonding with some dirty water and after 1st coat pretty quickly giving it another tight coat and flattening.

Only time I seen it was the other subby rough c**ts work but he was going over it when still wet as fook
 

ChrispyUK

Well-Known Member
Doing some subby work for a housing association currently kitchens and bathroom refits. Using a bag of bonding per kitchen roughly and not had one single issue with blistering over the backing coat. Knocking up the bonding with some dirty water and after 1st coat pretty quickly giving it another tight coat and flattening.

Only time I seen it was the other subby rough c**ts work but he was going over it when still wet as fook

You can do anything
But don’t you bleb
On my new skim coat
:inocente:

Uh huh


Thank you very much
 
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