Roughcast - The No-Nonsense Building Surveying & Damp Podcast
Oct 5, 2026 · 1 hr 3 min · 13 segments
In this episode, Dan welcomes Michiel Brouns, a paint expert known for his insights into historic building materials. With a rich background in historic building surveying, Michiel shares his journey…
Um, so a lime is literally made from, uh, from slaked lime, so you can make that really easily yourself.
Um, uh, it's, it's a really just reduced, um, very lightly pigmented wash. That's what it's called, lime wash.
And you set this up in really thin coats, and where you're actually brushing it on, you think that nothing is happening.
Um, and then when it starts to dry out, you start to get this pigmentation, uh, building up.
The temptation there can be you set it up too thick in one go because you think it's not really doing it.
A- and actually that's the case with pretty much all of these historic building materials.
It's not completely accurate, but it's, uh, casein is the, uh, is the protein, uh, that occurs in milk.
So if you, if you extract that, that becomes a really strong binder, um, which you can then, uh, mix with pigments and, and that becomes your, that becomes your interior paint predominantly.
I see now a lot of kind of silicate paints being recommended for like interior modern walls and everything.
It's gonna set so hard, especially on top of an existing emulsion, a modern emulsion, that it, it, it will fail.
Um, but, um, so it's about understanding these different, uh, the different aspects of these paints and what they actually do and can't do.
So the silicate paint is basic- That, that is one that completely binds chemically and mechanically with its substrate.
But if you set that up on like a, uh, a lime render for instance, or a, or a lime plaster, that sets too hard on the outside and then it can start to fail the, uh, uh, fail the lime underneath.
Um, so a lime is literally made from, uh, from slaked lime, so you can make that really easily yourself.
Um, uh, it's, it's a really just reduced, um, very lightly pigmented wash. That's what it's called, lime wash.
And you set this up in really thin coats, and where you're actually brushing it on, you think that nothing is happening.
Um, and then when it starts to dry out, you start to get this pigmentation, uh, building up.
The temptation there can be you set it up too thick in one go because you think it's not really doing it.
A- and actually that's the case with pretty much all of these historic building materials.
It's not completely accurate, but it's, uh, casein is the, uh, is the protein, uh, that occurs in milk.
So if you, if you extract that, that becomes a really strong binder, um, which you can then, uh, mix with pigments and, and that becomes your, that becomes your interior paint predominantly.
I see now a lot of kind of silicate paints being recommended for like interior modern walls and everything.
It's gonna set so hard, especially on top of an existing emulsion, a modern emulsion, that it, it, it will fail.
Um, but, um, so it's about understanding these different, uh, the different aspects of these paints and what they actually do and can't do.
So the silicate paint is basic- That, that is one that completely binds chemically and mechanically with its substrate.
But if you set that up on like a, uh, a lime render for instance, or a, or a lime plaster, that sets too hard on the outside and then it can start to fail the, uh, uh, fail the lime underneath.
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