More rendering!

Categories Uncategorized

Got the back wall done to head height – neither of us could bear the thought of climbing ladders on a Sunday. 🙂

My mixes are getting more consistent – did 6-7 mixer loads, and only one of them was noticeably on the dry side of ideal. The next one, of course, over-compensated and was nearly too wet, but the wet mix was still noticeably easier to spread on the wall.

Render mixes

(Disclaimer: this might all be wildly obvious to experienced renderers, but I’m recording it anyway for any newbies who, like me, like finding stuff out for themselves.)

Talking about render though – I’m doing a couple of things slightly differently from most of the workshops I’ve done recently. Most people seem dead set on using lime putty (which comes wet, in big 25kg goon bags) but I always wanted to try dry lime powder for a couple of reasons:

  • Lime putty, once you open a bag you kinda have to use the whole thing – you have to use it all or deal with the leftovers.
  • You also need a mixer big enough to make up the correct lime:sand ratio for the full bag, and my mixer isn’t that big.
  • The bags aren’t overly fragile, but you’re still lugging around a 25kg sack of kinda-liquid at a time, and that seems like a good way to make a mess.

Talking to an english plasterer at a workshop, he said that in the UK everyone uses dry hydrated lime (but over here it’s all putty, all the time) so it’s clearly possible to use dry lime. Reading one of my books, the main difference seems to simply be that lime putty gives a more workable mix?

So I’ve been mucking about with the dry powder – my first few batches were done by:

  1. Bucket of water in mixer (running, obviously)
  2. 4 shovels of lime into mixer
  3. 12 shovels of sand into mixer
  4. Add water to taste.

What seems to happen with this is the lime and water mix really fast (and basically turn into lime putty! – you get a lovely plastic’y layer of putty) in the bottom of the mixer, and then the sand kinda rumbles around on top not mixing with the lime unless you get a hand in there and scrape it out, and that is Not Fun.

Take 2:

  1. Bucket of water
  2. Four shovels of sand
  3. Four shovels each of lime and sand, interleaved one for one.
  4. Four shovels of sand
  5. Squirt some water around the bowl to wash the edges off (the dry lime does tend to wander a bit)

This way the weight of sand rolling around seems to stop the lime from congealing in the bottom. I can then leave this to mix while spreading the previous load (which got decanted into a wheelbarrow), and I’m consistently getting a workable mix out of it that seems to dry well – my earliest efforts have hardened nicely. I particularly noticed that today when scratching up the latest render – my scratcher wandered onto an older patch from a couple of weeks ago and it made absolutely no impact on the render at all.

Leave a Reply

Your email address will not be published. Required fields are marked *