The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 11-14-2002, 09:53 PM
El Zagna El Zagna is offline
Guest
 
Join Date: Jan 2001
How do they make black paint?

...or any other really dark color for that matter. Since you have to start with a white base, it would seem that the best you could do is some shade of gray.
Reply With Quote
  #2  
Old 11-14-2002, 10:02 PM
SlickRoenick SlickRoenick is offline
Guest
 
Join Date: Mar 2002
2 years ago an Ace Hardware paint dept. rep came in to talk to the boss and I over heard him say black paint has a black base. Red paints have red bases, and yellow paints have yellow bases. And now we stock different bases for certain colors. But we don't have black bases--not very high in demand
Reply With Quote
  #3  
Old 11-14-2002, 10:20 PM
happyheathen happyheathen is offline
BANNED
 
Join Date: Nov 2001
Posts: 2,394
"Paint" ain't white - unless white pigment has been added.
Reply With Quote
  #4  
Old 11-14-2002, 10:24 PM
Bob Scene Bob Scene is offline
Guest
 
Join Date: Oct 2000
You don't have to start paint with a white base. You can make black paint with just resin and carbon black, and use transparent filler pigments if you want a filler.
Reply With Quote
  #5  
Old 11-14-2002, 10:24 PM
astro astro is online now
Guest
 
Join Date: Jul 1999
History of Pigments

Quote:
BLACK

Black, first among the alchemical principals, is the action of fire. Charcoal was probably the first drawing tool. With white chalk and red earth colors, black formed the palette of prehistoric painters. Da Vinci counted black pigments among the most important to create tone, tint and shade. Tintoretto often under painted in black. While long associated with darkness and mourning, black has been a popular fashion color since the 16th century CE.

The making of the color "Elephantium" was first described in the 4th century BCE. Ivory scraps were tightly packed into clay pots, excluding as much air as possible. Covered with an iron lid, the ivory was heated in kilns to make ivory black. This very expensive process was used until 1929 when the last factory in Germany closed. Before the 20th century, various organic materials, including animal bones, were calcined together to form different colors of blacks. Neither the warm, purplish "vine black" made from vines, wine lees and grape skins, nor a bluish fruit stone black, made from burning pits, was completely lightfast.

At least since the time of the Neo-Impressionists there has been a controversy among painters about making greys. Thinking greys made from black are lifeless, some painters never allow black on their palettes. They only make greys from complements. Certainly overusing black in a painting will make it look dirty. But neutral greys made from black and white are the same as neutral greys made from exact complements. Greys made from complements are more lively because they are incomplete mixtures. The grey is created in the eye from an incomplete mixture of one color next to another.

In the 19th century better manufacturing methods for bone black yielded darker, more dense pigments that were less inexpensive. So bone black replaced genuine ivory black on artists' palettes. Essentially bone and ivory blacks are the same compounds of carbon and calcium, and pigment color and quality compare so favorably that artists' oil color made today from bone black is called Ivory Black. Ivory Black is a good, all purpose black that has a weak tinting strength and is slightly warm in its transparency. This is a good choice for mixing greys, tinting and mixing with other colors.

Mars Black is an artificial mineral pigment made from iron metal. It is well named for the god of war. Mars Black has approximately three times the tinting strength of Ivory Black and is very opaque. Cool in its masstone and strong, Mars Black is often the choice of the Neo-Expressionists and others who want make black opaque marks in thick wet paintings. It also is the leanest black and dries more quickly than Ivory. It is slightly warm in its tint. Mars Black is not as black a black as Ivory Black.

Van Dyke Brown is a warm black, which is completely lightfast, made from bone black and iron oxide. Payne's grey is the coolest black, made from Mars Black and Ultramarine Blue.

Copper Chromite Black made from the calcination of copper oxide and chromium oxide is a modern, more expensive black. This Copper Black is truly unique. Without the addition of painting mediums, it dries to a matte finish and looks like slate. Its tint may be the most appealing characteristic of Copper Chromite Black. Its tint is truly neutral.
Reply With Quote
  #6  
Old 11-14-2002, 11:18 PM
Nametag Nametag is offline
Charter Member
 
Join Date: Apr 2002
Location: California
Posts: 7,696
The blackest black pigment I've ever run across is iron oxide. I've used it in makeup and tattoo inks, and I've never seen anything better. I don't know whether they use it in paint, though. Iron oxide can be used to make a wide variety of shades: black, brown, red, umber, yellow. The yellow and red pigments are muted "rusty" versions, for the most part, but they are extremely stable and non-toxic. The different iron oxide pigments are characterized by their particle size.

White paint contains titanium dioxide (or zinc oxide, if it's cheap). While this improves its cover, and brightens blends made with it, it's not suitable for black paint and it's not used. The base for black paint is just the paint base: colorless solvents and resins, mostly.
Reply With Quote
  #7  
Old 11-14-2002, 11:54 PM
neutron star neutron star is offline
Guest
 
Join Date: Feb 2000
One chemical often used in paint, ink, toner, for coloring tires, and for numerous other uses, is carbon black, technically known as amorphous carbon. It's formed when a material containing carbon is burned without enough oxygen to fully burn. The leftover residue is a fine, black powder.

The stuff is a mess and a half, too. Ever seen copier toner? That's about what it looks like.

I work for a company that ships 10-20,000 pounds of carbon black every day. It's so fine that it seeps through the bags meant to hold it, and, given enough time, will deposit a black, hard-to-wash-off residue on everything in the vicinity.
Reply With Quote
  #8  
Old 11-15-2002, 12:07 AM
Bob Scene Bob Scene is offline
Guest
 
Join Date: Oct 2000
They do put iron oxide in paint. A lot of steel primers have red iron oxide in them because it inhibits corrosion. It makes an ugly color, but it doesn't matter for a bridge primer. When I was working in the highway department paint lab we were playing around with putting yellow iron oxide in the yellow road paint because we had had to take the lead chromate out of it and the organic pigments we were using were pretty transparent, so we were putting titanium in there for opacity, which caused the yellow stripes to look too white at night. The yellow iron oxide made the paint a nasty brown color in the daytime, but it was a really good yellow color at night. I don't know if or how they ever solved that problem.

All the black paint I ever worked with, which wasn't much, just had carbon black in it for color, but we were always doing almost industrial-type stuff where the appearance wasn't the most important thing.
Reply With Quote
  #9  
Old 11-15-2002, 06:51 AM
andy_fl andy_fl is offline
Guest
 
Join Date: Jun 2001
Quote:
Originally posted by Bob Scene
They do put iron oxide in paint.
There are two iron oxides :

1> Ferrite (Fe2O3) - Red or Reddish Brown
2> Magnetite (Fe3O4) - Black
Reply With Quote
  #10  
Old 11-15-2002, 11:30 AM
Nametag Nametag is offline
Charter Member
 
Join Date: Apr 2002
Location: California
Posts: 7,696
True, native magnetite is black, and is sometimes used for pigment, but the pigment called "iron oxide black" is ferrite. (Magnetite, by the way, is a mixture of Ferric Oxide (Fe2O3) and Ferrous Oxide (FeO).
Reply With Quote
  #11  
Old 11-18-2002, 08:55 AM
El Zagna El Zagna is offline
Guest
 
Join Date: Jan 2001
Thanks for everyone's responses, but I don't think we've got the answer yet. I was at Home Depot yesterday and I asked about their "dark tint" base, the stuff they use to make their dark colors. It is an off-white. So somehow they can take a gallon of off-white base paint, add a relatively small amout of pigment and make black - or at least near black. It must have something to do with the way the pigment molecules surround the other molecules... or something. I dunno.
Reply With Quote
  #12  
Old 11-18-2002, 05:43 PM
Nametag Nametag is offline
Charter Member
 
Join Date: Apr 2002
Location: California
Posts: 7,696
Sitting in a bucket, the stuff i off-white. If you paint it on the wall without having the colors mixed in, I think you will find that it dries clear (or maybe a little hazy).
Reply With Quote
  #13  
Old 11-18-2002, 06:44 PM
Bob Scene Bob Scene is offline
Guest
 
Join Date: Oct 2000
Quote:
Originally posted by bnorton
Thanks for everyone's responses, but I don't think we've got the answer yet. I was at Home Depot yesterday and I asked about their "dark tint" base, the stuff they use to make their dark colors. It is an off-white. So somehow they can take a gallon of off-white base paint, add a relatively small amout of pigment and make black - or at least near black. It must have something to do with the way the pigment molecules surround the other molecules... or something. I dunno.
We do have the answer. It's what I posted below. Any latex paint base is going to start out looking white or off-white, but that doesn't mean it won't dry clear.

What they're doing is what Nametag said. They have a paint base with latex (which is always called latex even though it's usually an emulsion of some other polymer like acrylic resin), water, additives and a clear pigment like talc or CaCO3. This stuff will look sort of off-white when it's a liquid, but will dry fairly transparent and colorless because opacity (hiding power) comes from the difference between the refractive index of the pigment and the refractive index of the medium it's dispersed in. The refractive index of talc or silica or CaCO3 is close enough to that of dry latex for it to make a fairly transparent film, but far enough from the refractive index of water to make the wet paint opaque. (Wet latex by itself is also white and opaque, of course.)

If your paint base only has transparent filler pigments in it, they may look white when it's wet, but they "disappear" when it's dry and don't affect the color noticeably. So if you put in dark tint colors, you'll get dark paint from something that started out looking white.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:38 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.