Cheap, UV neutral black paint - Black 2.0

[JMC]

I recently found myself needing a black paint that would be a) very absorbent of light, b ) as neutral as possible in the UV region (so as to have as little difference in reflection between 300nm and 400nm as possible), and c) be cheap and readily available. A chance conversation at work put me on to Black 2.0, which was a paint developed by a UK artist Stuart Semple (http://stuartsemple....k-art-material/). This is supposedly extremely matt black, and there's a fascinating story behind the development of it, which is highly typical of the art world (it was developed to provide the wider art world a really black paint, after a UK company developed something called Vantablack which absorbs more than 99% of light, and then restricted who could buy it to scientists and one artist in the UK).

 

Anyway enough of the back story - just how black is it? Given I have access to a nice UV Vis spectrometer I got hold of a sample of this material, painted it onto some white card, and compared the amount of light it reflected to a the black tile on a X-rite/Gretag Macbeth Colour Checker chart (old version, pre November 2014). And this is what it looks like;

 

I was very surprised to see it reflected less light than the X-rite/Gretag Macbeth Colour checker chart black (GM black in the graph), and that in the 300-400nm range it was actually more neutral in its reflective properties than the Colour Checker chart black. Needless to say I was very impressed with it, as it fitted my key requirements (neutral, low reflectivity, cheap and readily available), oh and it smells of cherries too. All for the princely sum of £12 for 150ml, which they reckon is enough to cover about 1-1.5m2.

 

This was measured on a Perkin Elmer Lambda 650S UV-Vis spectrometer (150mm integrating sphere) between 250nm and 800nm (1s collection time per nm).

[Andy Perrin]

Semple reportedly put quite a bit of effort into developing that Black 2.0. I'm surprised it works so well in UV! Especially given how cheap it is and that Semple, as an artist, would care only about visible light. I have a piece of Acktar Metal Velvet, and they claim it is in the <1% reflected range in UV, but at a VERY high price (per unit area).

[Daryll]

Just ordered a tube , going to paint a piece of ply for a backdrop for flowers etc

[Oliver Krohn]

Really interesting! Did someone try to mix it with barium sulfate or something else to obtain a standard series?

[JMC]

I ordered some PTFE powder to try mixing with this but unfortunately it was stopped by UK customs and returned to sender, so I forgot about it. I've not thought about trying the BaSO4 though.

[Cadmium]

Have you tried the Krylon 1602 ultra flat black?

[JMC]

Quick update on this one. I've been happily using Black 2.0 paint for various projects over the last year and half, and have been very impressed with it. I heard recently that they were developing an even blacker version - Black 3.0 - and ordered one of their samples to test. It arrived today, and I have prepared a test sample to image, and compare against my Labsphere 2% and 5% diffuse reflectance standards, and against the old Black 2.0. Unfortunately I do not have access to the spectrometer I used before for the scans above anymore, so it'll be comparison images this time. Even visually, while drying, the Black 3.0 is looking even darker than the original 2.0 version, which bodes well. I shall post images when I have got them sorted.

[Cadmium]

oops, I already said that, sorry, delete this message.

[rfcurry]

I have some single-wall carbon nanotubes in a binder that should get down at least that far. I don't have an integrating sphere to test it with. However, I have some ceramic oxides that reflect less than 3% in the UV but are so small (<10nm particle size) that they are transparent in wavelengths >400nm. (See the images below Vis/NIR/UV. The wearer's right side of his uniform has been treated with my UV camo.)

 

http://uvrdefensetech.com/images/VisIRUVUVP.jpg

 

If I treat half the Vis white panels of a ColorChecker with my 3% UVRC, it should give me a dependable UV standard for those days when dandelions are not available. :)

[JMC]

Steve, in answer to your previous question, no I have not tested the Krylon paint.

 

Reed, very interesting. I miss my spectrometer with the integrating sphere. What I have now are some diffuse reflectance disks with different reflectances. At least I can get some relative data that way.

[dabateman]

Reed,

That looks really cool.

Having a standard for uv would be great. I was thinking the colour checker would work. But haven't played with one yet. I just got a cheap one on the ebay 10% off day. So hopefully it will arrive this week.

I also want to see if the colors vary with wavelength.

 

Jonathan,

Sorry to here your spectrometer is gone. Thank you for all the spectrums you have provided. Have been very helpful.

 

[JMC]

David, I've lost the fancy spectrometer, so no more reflectance measures. I can still to transmission though with my Ocean Optics one. Colour checker doesn't work for UV. The grey tiles, have a very non linear reflectance profile in the UV. Not sure about the colour tiles though, never checked those.

[JMC]

The image below was taken on my monochrome 5DSR, using the 85mm UAT lens (at f8), and a Baader U filter in daylight (no direct sun). The top line has the 2 Black paints - the original Black 2.0 and the new Black 3.0. The bottom has a black tile from an Xrite colour checker chart, and 2 diffuse reflectance standards from Labsphere - 5% and 2%. The image is obviously very over exposed to look for differences between the blacks. This is just a crop from the jpeg, but I also took the RAW files.

 

The new Black 3.0 is darker than the original 2.0 (so is reflecting less UV), although it is perhaps a little hard to see here. Using the RAW file I opened an image of the them in Rawdigger and extracted the red, green and blue values, and then averaged them for each of the 5 standards. I got the following;

 

Black 2.0______ 5564

Black 3.0______ 4748

Colour checker__ 5919

Labsphere 5%__ 8280

Labsphere 2%__ 3604

 

The Black 3.0 is darker than the original 2.0. Based on the numbers for the 2% and 5% Labsphere diffuse reflectance standards, the original Black 2.0 was reflecting about 3.2% and the new Black 3.0 about 2.7%. Both of the tiles reflect less UV than the Colour checker black tile. My numbers here are slightly different to the actual measured reflectances above, but they were done on a spectrometer, and not be simply analysing an image.

 

I used 4 coats of paint for each square - about 1 hour between each one - and then left it to dry for 24 hours. They were painted onto white cardboard.

 

All in all a good paint for a low reflectance coating. When it comes out officially the new Black 3.0 should give almost as dark a surface as a 2% Spectralon tile, for a fraction of the cost. I've also used the original Black 2.0 as a low fluorescence background too, although I have yet to try the new version for that.

[ulf]

The Black 2.0 is supposed to be possible to use with airbrush application too after diluting it with water.

That gives a more even surface.

 

I tried airbrushing Black 2.0 mixed with barium sulphate when experimenting a bit, trying to make an UV-even grey tile.

The surface was quite nice and even, but I had no way of verifying any reflective spectrum.

[Andrea B.]

If overexposure were linear, then it might make some sense to overexpose in order to detect differences between the blacks. But the whole thing is so not linear - that is, both exposures and/or over-exposures. Sometimes overexposure can really mess up or lose the data, and it cannot always be recovered by pulling back the exposure slider in the converter.

 

So perhaps a correct exposure together with the sampled Raw DIgger readings might better show and measure the differences between the blacks? Of course, not having done this experiment myself I cannot say with certainty that that would be the case. :)

 

BTW, what overexposure levels did Raw Digger show anyway?

[JMC]

If overexposure were linear, then it might make some sense to overexpose in order to detect differences between the blacks. But the whole thing is so not linear - that is, both exposures and/or over-exposures. Sometimes overexposure can really mess up or lose the data, and it cannot always be recovered by pulling back the exposure slider in the converter.

 

So perhaps a correct exposure together with the sampled Raw DIgger readings might better show and measure the differences between the blacks? Of course, not having done this experiment myself I cannot say with certainty that that would be the case. :)

 

BTW, what overexposure levels did Raw Digger show anyway?

 

Hi Andrea, Not been ignoring you, just got back from 2 weeks in Tasmania with very limited internet. The overexposure indicator in RawDigger, basically showed everything in the background (white areas) as overexposed. Thankfully when I took the images, I captured some at lower exposure too. If I look at one with much lower exposure in RawDigger as a RAW composite file, where the background isn't overexposed, I get the following;

 

Black 2.0______ 694

Black 3.0______ 592

Colour checker__ 739

Labsphere 5%__ 1028

Labsphere 2%__ 456

 

So, the same rankings as before. The Black 3.0 paint is darker than the 2.0, but doesn't quite get down to the 2% diffuse reflectance standard (although both paint standards are much darker than the 5% standard and darker than the Colour checker black tile).

 

As I understand it the Black 2.0 is currently available and the 3.0 is due for release later in 2019 (around May time according to their website).