chemistry of color /colorants (ch..14)

Question 1

what are colorants?

Answer 1

in Forensic interest… are in dyes and pigments and are applied to fibers,inks,paint

Question 2

where does color arise ?

Answer 2

chemical structure; conjugated systems

Question 3

T/F it is hard to quantitate color

Answer 3

T

Question 4

humans can sense EM radiation from____

Answer 4

380-700nm

Question 5

response to receptor cells in the ___

Answer 5

retina

Question 6

the __ are responsible for night and peripheral vision

Answer 6

rods

Question 7

__ provide color sensing

Answer 7

cones

Question 8

what are the 3 types of cones ?

Answer 8

red,green, and blue (RBG)

Question 9

how does the CIE system express findings?

Answer 9

using X and Y derived from a reflective spectrum that is a combination of the primary spectrum

Question 10

what is the goal of CIE ?

Answer 10

to express color as a weighted average of RGB and convert to be plotted in 2 dimensions

Question 11

what is the Munsell system ?

Answer 11

(Albert Munsell)
- similar to CIE
uses the three variables : hue,brightness, and saturation

Question 12

Munsell charts are used in forensic analysis of ___ and ___

Answer 12

paints and soils

Question 13

CMY system (____) is used for ___

Answer 13

cyan-magenta-yellow
printers

Question 14

RGB (____) is used for ___

Answer 14

red-green-blue
monitors

Question 15

when do we use colorants ?

Answer 15

analytical chemistry : use of dyes as acid/base indicators
histological stains: used in the biological disciplines are dyes

Question 16

what is the difference between pigments and dyes ?

Answer 16

** dyes will penetrate a paper with solvent, pigments in paint dry on top**
- solubility ; dyes are soluble in solvent they are carried
- dye has an affinity for their substrate, pigments do not

Question 17

T/F pigments are suspended particulates

Answer 17

true

Question 18

T/F pigments are nonmetallic

Answer 18

F: they are metallic and contain a transition metal , some are organic

Question 19

Ink consists of __

Answer 19

solvent, colorants(dyes/pigments/both), and other additives (to control thickness and appearance when dried)

Question 20

what inks are used for ink formulations ?

Answer 20

methyl , methyl ketones, isophorone, and glycol ethers

Question 21

different types of inks:

Answer 21

printing ink, ballpoint pen ink, gel pen inks, typing ribbons

Question 22

___ used to stabilize the double layer of pigments

Answer 22

surfactants

Question 23

what resins control the viscosity ?

Answer 23

adhesives

Question 24

what is the oldest ink?

Answer 24

carbon ink (India ink)

Question 25

what is the dot matrix printer?

Answer 25

like a typewriter, uses an impact method to create letters by striking paper through an inked ribbon (series of dots)

Question 26

which printers are non - impact ?

Answer 26

laser printers, photocopiers, and ink-jet printers laser: rotation drum surface , scanning the grid ink: similar to dot except the ink is sprayed

Question 27

what is toner

Answer 27

toner is a dry powdery material that contains waxy plastic and colorant

Question 28

toner cartridges include :

Answer 28

black, yellow, magenta, and cyan (CMY)

Question 29

what does a toner do?

Answer 29

(-) charged toner applied to the drum and adheres, paper with a charge is rolled on the drum --> transferring toner from drum to paper (by heat which melts the waxy toner)

Question 30

what is the purpose of mechanical printing?

Answer 30

we use this for dollar bills (which is hard to recreate through counterfeiters)

Question 31

process of mechanical printing?

Answer 31

- cast of the dye made of plastic (alto) - placed in electrolyte solution - plate is coated with ink - special paper is rolled across the plate to transfer the ink on the surface ; acquiring ridges and grooves

Question 32

ancient paints used ___ as binding agents

Answer 32

beeswax and fats

Question 32

what are the 3 elements of paints

Answer 32

solvent (organic or water)which evaporates, a colorants (pigment), and binding agent that polymerizes during curing stage

Question 32

T/F paints can be cured unassisted

Answer 32

T ; or even by UV/heat

Question 33

paint on a porous or nonporous system use a layer system: what is that process?

Answer 33

- a primer Is added (prepare the substrate) - the colorants layer is added (dye/pigment) - protective layer of varnish or clear coat

Question 34

latex paints are water based but have challenges since__

Answer 34

binders and resins are not soluble but used as micelles; surround and dissolve monomers (which polymerizes)

Question 35

once the latex paint is applied to the substrate ...

Answer 35

the water evaporates and allows the polymerization to proceed to completion

Question 36

T/F cars are painted in a complex layering system

Answer 36

T: can be used to differentiation 2 systems

Question 37

*** know 3 layer method she has on page 6 ***

Answer 37

and do study guide !!!!!!!