White Dye
han...@quick.net
-=-=-
There are water soluble or oil/solvent soluble dyes available in every
conceivable shade of the rainbow, from a faint yellow to a dark violet. Even
black.
But there seems to be no such dye with which you can color an object
porcellain WHITE. In fact, there seem to be no white dyes at all. Or are
there?
Sure, there are plenty of white pigments available, but why is there no
soluble white dye?
So, is there a fundamental scientific reason, a phys / chem / optical reason,
for the lack of white, water soluble or oil/solvent soluble dyes?
Thanks,
hanson
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Doug Barr
so how could you have a white one (i.e. _all_ incident light is reflected)?
Pigments can appear white (e.g. titanium dioxide) bacause they reflect
(nearly) all incident light, their spectral absorbance lying outside the
visible region.
regards,
Doug.
John_
>So, is there a fundamental scientific reason, a phys / chem / optical reason,
>for the lack of white, water soluble or oil/solvent soluble dyes?
A solution of a red dye is red because it transmits red light. A solution of a 'white
dye' would transmit white light. Water would be a reasonable approximation to such a
dye.
John_
Andreas Gosberg
The best you can get is a white pigment, or more precisely: a pigment appearing
white.
regards,
a.g.
han...@quick.net wrote:
> Are there truly water soluble, non pigmented white dyes available?
> -=-=-
> There are water soluble or oil/solvent soluble dyes available in every
> conceivable shade of the rainbow, from a faint yellow to a dark violet. Even
> black.
>
> But there seems to be no such dye with which you can color an object
> porcellain WHITE. In fact, there seem to be no white dyes at all. Or are
> there?
>
> Sure, there are plenty of white pigments available, but why is there no
> soluble white dye?
>
> So, is there a fundamental scientific reason, a phys / chem / optical reason,
> for the lack of white, water soluble or oil/solvent soluble dyes?
>
b.h.j...@hw.ac.uk
Statistically, I suppose, black and white paints must be the most
expensive? Considering the number of colours to be obtained cheaply with
naturally occurring substances. (Why are we taught to despise anything
which is dug up OUT of the earth? It's only old trees.)
On 1998-09-04 bar...@NOSPAMTHANKYOU.bp.com said:
`Newsgroups: sci.chem,sci.engr.color,sci.optics,sci.physics
`hmmm...I always thought that dyes _absorb_ light (hence providing
============ ===== ===== BILL J. ===== ===== ============
GM8APX, qthr Edinburgh, Scotland, UK
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Uncle Al
>
> Are there truly water soluble, non pigmented white dyes available?
> -=-=-
> There are water soluble or oil/solvent soluble dyes available in every
> conceivable shade of the rainbow, from a faint yellow to a dark violet. Even
> black.
>
> But there seems to be no such dye with which you can color an object
> porcellain WHITE. In fact, there seem to be no white dyes at all. Or are
> there?
>
> Sure, there are plenty of white pigments available, but why is there no
> soluble white dye?
>
> So, is there a fundamental scientific reason, a phys / chem / optical reason,
> for the lack of white, water soluble or oil/solvent soluble dyes?
>
> Thanks,
> hanson
A dye is a soluble material that manifests an optical absorption, the
residual EM radiation being perceived as the color. As "white" cannot
be generated by subtraction, there are no white dyes.
You can have a fluroescent white dye, absorbing and re-emitting.
Pigment (CaCO3, ZnO, especially TiO2) gives you a scattered white.
--
Uncle Al Schwartz
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Dr. Henry
optical brightners that are stilbene based products. They
basically coat the fibers as a finish and reflect all light,
therefore they look white.
--
Dr. Henry Boyter, Jr. Ph.D. Chemist
The opinions of Dr. Boyter are provided for informational
purposes only and should not be used as advice. No
warranty or expression of professionalism is implied.
**********************************************************
Uncle Al wrote in message <35EFE9...@ix.netcom.com>...
Jim Deutch
of light, giving the substance color. It is always at least partially
transparent (you can see detail of the original surface still after it is
dyed). A "white dye", therefore, is an oxymoron. To turn a colored
surface white, you must cover it with an _opaque_ white substance: that's a
pigment, not a dye.
Jim Deutch
han...@quick.net wrote in article <6snjhk$31f$1...@nnrp1.dejanews.com>...
George Battrick
How about using bleach?
George
Joe Gwinn
white implies the absence of absorption. One can bleach the surface color
out, or cover it up with a solid pigment (such as titanium dioxide), or a
bit of both.
Joe
donald haarmann
han...@quick.net wrote in message <6snjhk$31f$1...@nnrp1.dejanews.com>...
>Are there truly water soluble, non pigmented white dyes available?
[snip]
>But there seems to be no such dye with which you can color an object
>porcellain WHITE. In fact, there seem to be no white dyes at all. Or are
>there?
>
>Sure, there are plenty of white pigments available, but why is there no
>soluble white dye?
[snip]
Sure there is. The person who invented the "DASER" (darkness amplification by
stimulated
emission of radiation) patented a white dye. Sorry to say -- I cannot remember
their
name.
donald j haarmann
------------------------------------
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Mervyn Stockwood (Attrib.)
Modem
GW>white implies the absence of absorption. One can bleach the surface color
GW>out, or cover it up with a solid pigment (such as titanium dioxide), or a
GW>bit of both.
GW>Joe
Well, if you add pine oil ( a clear liquid) to water (another clear
liquid) you get a milky whit liquid. Is that what you mean?
Marvin Margoshes
That gives you a suspension of droplets of one liquid in another. The two
liquids have different refractive indices, so the droplets scatter light.
The sacttered light looks white, but it isn't actually because the shorter
wavelengthjs of light (blue) are scattered more than the longer wavelengths
(red). The suspension doesn't fit the definbition of a dye, which others
have already given in this NG.