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solway

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I'm after doing a few sample panels at home here with traditional sand and cement. 1st mix was 5 sand 1 cem and half lime with 200ml evoplast waterproofer mixed into a 10 litre bucket of water

2nd mix was 4 1/2 sand 1 cem and half lime to 200ml waterproofer mixed into 10 litre bucket of water

Both mixes were lovely and creamy.

I did these samples because I seem to get hailine cracks on sponge finish render but no hairline cracks on "napped render"

So on the panels I did at home I sponged half and napped the other half and guess what......when I throw water onto the panels that I sponge finished it shows hairline cracks but the napped finish is perfect (no hairlines) The hairlines are evident as soon as they recieve water but after 20 or 30 seconds as the water soaks in and dries out again they can't be seen. Why do the hairlines show up on sponged finish more than napped finish. I know it's shrinkage but is this the norm when it comes to sponge finish. Really annoying...
 
I'm after doing a few sample panels at home here with traditional sand and cement. 1st mix was 5 sand 1 cem and half lime with 200ml evoplast waterproofer mixed into a 10 litre bucket of water

2nd mix was 4 1/2 sand 1 cem and half lime to 200ml waterproofer mixed into 10 litre bucket of water

Both mixes were lovely and creamy.

I did these samples because I seem to get hailine cracks on sponge finish render but no hairline cracks on "napped render"

So on the panels I did at home I sponged half and napped the other half and guess what......when I throw water onto the panels that I sponge finished it shows hairline cracks but the napped finish is perfect (no hairlines) The hairlines are evident as soon as they recieve water but after 20 or 30 seconds as the water soaks in and dries out again they can't be seen. Why do the hairlines show up on sponged finish more than napped finish. I know it's shrinkage but is this the norm when it comes to sponge finish. Really annoying...
Wrong mix.
@Casper thoughts??
 
Good question I think?
Reckon the answer is something to do with more even distribution of water left in the mix when napped?
 
Interesting answer monkey boy but how would you evenly distribute water evenly over a sponge finish to achieve no hairlines. Its sponged with a damp sponge
 
Interesting answer monkey boy but how would you evenly distribute water evenly over a sponge finish to achieve no hairlines. Its sponged with a damp sponge
Try using the handle sponge on both set of it makes a difference???
 
Cockney has answered your question you want to avoid hairline cracks put fibres in
But why didn't the napped render have hairlines.....same mix. I'd guess 99% of plasterers don't put fibres in their render when sponge finishing. If it's the wrong mix for sponge finish I'm all ears
 
I'm after doing a few sample panels at home here with traditional sand and cement. 1st mix was 5 sand 1 cem and half lime with 200ml evoplast waterproofer mixed into a 10 litre bucket of water

2nd mix was 4 1/2 sand 1 cem and half lime to 200ml waterproofer mixed into 10 litre bucket of water

Both mixes were lovely and creamy.

I did these samples because I seem to get hailine cracks on sponge finish render but no hairline cracks on "napped render"

So on the panels I did at home I sponged half and napped the other half and guess what......when I throw water onto the panels that I sponge finished it shows hairline cracks but the napped finish is perfect (no hairlines) The hairlines are evident as soon as they recieve water but after 20 or 30 seconds as the water soaks in and dries out again they can't be seen. Why do the hairlines show up on sponged finish more than napped finish. I know it's shrinkage but is this the norm when it comes to sponge finish. Really annoying...
Was it over a scratch coat if so the top coat needs to be weaker
 
your first post states 5-1 first coat second coat 4-1.
Hi Malc. No the 2 mixes I mentioned in the 1st post went on over a 4-1 scratch coat.
I firstly scratched the panel at 4-1 on a Saturday and the following Saturday I finish coated the panel (divided the panel in half with 2 different finish coat mixes)
 
,,,,,,1st mix was 5 sand 1 cem and half lime with 200ml evoplast waterproofer mixed into a 10 litre bucket of water

2nd mix was 4 1/2 sand 1 cem and half lime to 200ml waterproofer mixed into 10 litre bucket of water

Both mixes were lovely and creamy
 
Hi Malc. No the 2 mixes I mentioned in the 1st post went on over a 4-1 scratch coat.
I firstly scratched the panel at 4-1 on a Saturday and the following Saturday I finish coated the panel (divided the panel in half with 2 different finish coat mixes)

did you use sharpe sand? if the sand is to soft it will crack.
when i look at the so called plastering sand at builders merchants it looks to soft. the sand does need a grit in it to produce any strength.
 
Ya sand is lovely and clean. Good "bite" to it. Its very strange because over the last 2 years we were on a site doing houses which had a napp finish. Over the 2 years I never saw a hairline on any of the houses or boundary walls. Religiously used the 5 to 1 mix as stated above all through the site work. Same sand used throughout also. But whenever I left the site to do other houses which were sponge finished 9 times out of 10 they resulted in hairlines. I used the same sand as the site and same mix as the napped.
 
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