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Yeah it’s white but does dust and debris still stick to it? If it does, it’ll only be really effective until the next cleaning... and then probably just as goo

Yeah it’s white but does dust and debris still stick to it? If it does, it’ll only be really effective until the next cleaning... and then probably just as good as plain white paint.

adrian_b 6y ago
They said that they have used an acrylic binder, so this white paint should behave like any other acrylic paint, so it should need periodic cleaning. What is novel is that they have discovered some new method for preparing the barium sulfate pigment and mixing it with the binder, which allows very small pigment particles, possibly having a certain form, and also a very large ratio between the quantities of pigment and binder in the paint.
- adrian_b 6y ago
  Now I have read an earlier version of this paper, which is freely available: https://arxiv.org/abs/2011.01161 https://arxiv.org/abs/2011.01161 The main points are: 1. The more common white pigment titanium white is not good for cooling something exposed to sun, because it strongly absorbs ultraviolet light. (Besides generating heat, this ultraviolet absorption also causes photo-chemical reactions that degrade in time the organic paint binders.) 2. So they have chosen barium sulfate, which reflects not only visible light, but also ultraviolet and near infrared. 3. Barium sulfate not only reflects solar light, but it also emits efficiently in the far infrared, which cools the painted surface. 4. Barium sulfate was traditionally considered a worse white pigment, because it has a lower refractive index than other pigments, like titanium white. 5. The Purdue University team has overcome this disadvantage of barium sulfate by designing a manufacturing process for the pigment that not only ensures a very small average pigment particle size but also a broad distribution of the particle sizes, which results in good reflection properties over the entire solar spectrum.
dredmorbius 6y ago
Right. The notion of painting roofs white to increase albedo is an old one (look up "Whitecap", which I was familiar with about 30 years ago). And the practical limit is of behaviour in the environment: dirt, grime, damage (hail, wind, birds, insects, ultraviolet light, etc.). It's unlikely that a "whitest white" substance will also be optimised for those characteristics. But a durable, easily-cleaned, reflective surfacing material could prove useful. It's all but certain that the actual applications for this material won't be as roofing. At least not for standard construction.

Yeah it’s white but does dust and debris still stick to it? If it does, it’ll only be really effective until the next cleaning... and then probably just as good as plain white paint.

adrian_b 6y ago

They said that they have used an acrylic binder, so this white paint should behave like any other acrylic paint, so it should need periodic cleaning. What is novel is that they have discovered some new method for preparing the barium sulfate pigment and mixing it with the binder, which allows very small pigment particles, possibly having a certain form, and also a very large ratio between the quantities of pigment and binder in the paint.

adrian_b 6y ago
Now I have read an earlier version of this paper, which is freely available: https://arxiv.org/abs/2011.01161 https://arxiv.org/abs/2011.01161 The main points are: 1. The more common white pigment titanium white is not good for cooling something exposed to sun, because it strongly absorbs ultraviolet light. (Besides generating heat, this ultraviolet absorption also causes photo-chemical reactions that degrade in time the organic paint binders.) 2. So they have chosen barium sulfate, which reflects not only visible light, but also ultraviolet and near infrared. 3. Barium sulfate not only reflects solar light, but it also emits efficiently in the far infrared, which cools the painted surface. 4. Barium sulfate was traditionally considered a worse white pigment, because it has a lower refractive index than other pigments, like titanium white. 5. The Purdue University team has overcome this disadvantage of barium sulfate by designing a manufacturing process for the pigment that not only ensures a very small average pigment particle size but also a broad distribution of the particle sizes, which results in good reflection properties over the entire solar spectrum.

dredmorbius 6y ago

Right. The notion of painting roofs white to increase albedo is an old one (look up "Whitecap", which I was familiar with about 30 years ago). And the practical limit is of behaviour in the environment: dirt, grime, damage (hail, wind, birds, insects, ultraviolet light, etc.). It's unlikely that a "whitest white" substance will also be optimised for those characteristics. But a durable, easily-cleaned, reflective surfacing material could prove useful. It's all but certain that the actual applications for this material won't be as roofing. At least not for standard construction.