I spent some time researching the NeXT Black color specification to put together a new written spec for repainting Cubes. The original NeXT Black color specification (
https://www.nextcomputers.org/forums/index.php?topic=136) defines the color using the older Hunterlab color standard. Years ago the NeXT community worked on defining a paint specification for repainting NeXTcubes, and that specification ended up being the Sherwin-Williams product number that we see in the forums here. The problem with that specification is that not everyone has access to Sherwin-Williams paint, and the color as well as the surface smoothness varied slightly from the paint used on original Cubes. It makes sense to define the color itself rather than a product number from one paint company. This thread documents the NeXT black color in multiple color standards so that paint shops can mix the color using paint from various manufacturers. We'll also create a separate Sherwin-Williams paint specification for those who have access to their paint.
NeXT chose the Hunterlab color standard, also known as the HunterLab L, a, b color scale. HunterLab updated the scale in 1966 to use the CIE 10° observer angle (field of view), which was released in 1964. The goal here is to convert the Hunterlab L, a, b color specification provided by NeXT to the CIELAB L*, a*, b* specification which is more commonly in use today. Fortunately Hunterlab has a webpage (
https://support.hunterlab.com/hc/en-us/articles/202023905-Is-there-an-Internet-Site-for-converting-and-displaying-color-values) that recommends using the EasyRGB web site (
http://www.easyrgb.com/en/convert.php) for converting from one color scale to another. The NeXT black color specification is missing a few elements to fully define the color. It doesn't specify a value for the Illuminate, so Hunterlab recommends using the most common one which is D65 (daylight). The NeXT spec also doesn't mention the measuring instrument Geometry and Mode; however Hunterlab recommends using the common Directional 0°/45° reflectance spec. With all of this information the NeXT color specification can be documented in both the Hunterlab and CIELAB color standards using the EasyRGB web site.
NeXT Black Color SpecificationNeXT Black Color Specification
Color Scale Color Values Illuminant Observer Instrument Geometry and Mode
=============================================================================================================
HunterLab L, a, b 27.8 -0.25 -1.39 D65 (daylight) 10° (1964) Directional 0°/45° reflectance
CIELAB L*, a*, b* 33.411 -0.372 -2.083 D65 (daylight) 10° (1964) Directional 0°/45° reflectance
GLOSS = 13° ±3°
DE (ΔE) = ±0.5
This color specification has not been tested yet so use this information at your own risk. Let us know if you have paint mixed with the specification and any feedback that you get from the company that mixes the paint. The end result of using a color specification is subjective, so let us know what you think of the results. I'll update this specification if necessary as I get feedback.
NeXT Black Paint SpecificationNext a new Sherwin Williams paint can be defined that more accurately represents the original color and smoothness. Sherwin Williams offers a smoother paint than what they recommended to us 20 years ago. The old paint was the Kem Aqua 600T, which has a slight texture. The new paint is the Kem Aqua 600 Smooth Water Reducible Enamel. This paint was developed for computer enclosures and provides a smooth finish. It should be noted that this paint has not been tested on a NeXTcube yet. The information here should be used at your own risk. I'll update this paint specification as well as I get your feedback.
Paint: Sherwin-Williams Kem Aqua 600 Smooth Water Reducible Enamel (
https://industrial.sherwin-williams.com/na/us/en/general-industrial/catalog/product/general-industrial-coatings/products-by-industry.11543145/kem-aqua-600-smooth-water-reducible-enamel.9197780.html) | Datasheet (
https://www.paintdocs.com/docs/webPDF.jsp?SITEID=SWPCGIND&doctype=PDS&prodno=035777244203&lang=2)
Primer: Sherwin-Williams Polane W2 Primer E61A516 (
https://industrial.sherwin-williams.com/na/us/en/general-industrial/catalog/product/general-industrial-coatings/products-by-industry.11543145/polane-w2-primer.9197974.html) | Datasheet (
https://www.paintdocs.com/docs/webPDF.jsp?SITEID=SWPCGIND&doctype=PDS&prodno=035777205020&lang=2)
Filler Primer: Sherwin-Williams Kem Aqua 65P SprayFil (
https://industrial.sherwin-williams.com/na/us/en/general-industrial/catalog/product/general-industrial-coatings/products-by-industry.11543145/kem-aqua-65p-water-reducible-sprayfil.9197782.html) | Datasheet (
https://www.paintdocs.com/docs/webPDF.jsp?SITEID=SWPCGIND&doctype=PDS&prodno=035777425206&lang=2)
Color Specification References:https://support.hunterlab.com/hc/en-us/articles/202023905-Is-there-an-Internet-Site-for-converting-and-displaying-color-values (
https://support.hunterlab.com/hc/en-us/articles/202023905-Is-there-an-Internet-Site-for-converting-and-displaying-color-values)
http://www.easyrgb.com/en/convert.php#inputFORM (
http://www.easyrgb.com/en/convert.php#inputFORM)
http://www.easyrgb.com/en/math.php (
http://www.easyrgb.com/en/math.php)
https://support.hunterlab.com/hc/en-us/articles/204137825-Measuring-Color-using-Hunter-L-a-b-versus-CIE-1976-L-a-b-AN-1005b (
https://support.hunterlab.com/hc/en-us/articles/204137825-Measuring-Color-using-Hunter-L-a-b-versus-CIE-1976-L-a-b-AN-1005b)
https://www.hunterlab.com/blog/what-is-cielab-color-space/ (
https://www.hunterlab.com/blog/what-is-cielab-color-space/)
https://support.hunterlab.com/hc/en-us/categories/201319586-Color-Theory (
https://support.hunterlab.com/hc/en-us/categories/201319586-Color-Theory)
https://en.wikipedia.org/wiki/International_Commission_on_Illumination (
https://en.wikipedia.org/wiki/International_Commission_on_Illumination)
https://en.wikipedia.org/wiki/CIELAB_color_space (
https://en.wikipedia.org/wiki/CIELAB_color_space)
https://en.wikipedia.org/wiki/Hunter_Lab (
https://en.wikipedia.org/wiki/Hunter_Lab)