Air blisters in k rend

[Creedon93]

Sponge finishing white k rend, floats up perfectly but noticed a few small air blister when sun shines on it, wall was scratch coated with sand and cement and top coat k rend, pulled serrated edge on it and straightened second coat with straight edge, what causes this?

 

[John j]

Sponge finishing white k rend, floats up perfectly but noticed a few small air blister when sun shines on it, wall was scratch coated with sand and cement and top coat k rend, pulled serrated edge on it and straightened second coat with straight edge, what causes this?

Air

 

[MIXERMAN]

Photo please. Thought you shouldn't use sand and cement scratch coat with k rend stuff.

 

[Monkey Boy]

Thought you shouldn't use k rend stuff.

fixed that for you

 

[Too much mortar mix]

Getting alot of it in sand and cement render lately sponge finish..some sand seem worse than others for it.

 

[bobski]

Background, dampened?

Scratched properly?

Size of trowel, compression not pressed in hard enough, (sometimes using a big trowel)

Or was it sprayed on?

 

[Too much mortar mix]

In our case scratch with a stiff brush and then a scratcher. Walls r wet according to weather and conditions, wen floating and esp sponging can see the air bubble in top coat which hasn't keyed to the scratch. 13 inch carbon hand applied. Little additives in mix, lime and small bit mortar mix in top coat gear does b raw enough. Fibres and mortar mix in scratch and cap full of sbr to 3 bags of cement in mixer for scratch.

 

[CeeVee]

Always used to get this when not spraying it on.
Guessed it was just a 'hand applying' thing.

 

[Creedon93]

It was scratched properly and the perfect thickness left for top coat, the rest of the house is perfect its just this one patch, it was hand applied, k rend I relatively new to us its mostly sand and cement we work with, how long should the k rend be left sit after pulling serrated edge on it?

 

[bobski]

In our case scratch with a stiff brush and then a scratcher. Walls r wet according to weather and conditions, wen floating and esp sponging can see the air bubble in top coat which hasn't keyed to the scratch. 13 inch carbon hand applied. Little additives in mix, lime and small bit mortar mix in top coat gear does b raw enough. Fibres and mortar mix in scratch and cap full of sbr to 3 bags of cement in mixer for scratch.

It was scratched properly and the perfect thickness left for top coat, the rest of the house is perfect its just this one patch, it was hand applied, k rend I relatively new to us its mostly sand and cement we work with, how long should the k rend be left sit after pulling serrated edge on it?

Both cases,

Used to get that with sand that is not that great.

When we've had that when hand applying this final coat, is to mix creamy, press a very tight coat in - really press it into every void, and then to glide one straight over the top. (Straight after while still wet.)


Obviously depending on wall size and man power, will determine timings.

 

[woodeneye]

Sponge finishing white k rend, floats up perfectly but noticed a few small air blister when sun shines on it, wall was scratch coated with sand and cement and top coat k rend, pulled serrated edge on it and straightened second coat with straight edge, what causes this?

You didn't follow the system...

 

[woodeneye]

Laying on too quick and no agitation in your trowel action. All about the wiggle push the air out. Also happens when making your second pass too soon.