Printing ink formulation Flashcards
What is the definition of dyeing?
Dyeing involves the transfer of dyes from solution in water into a textile fibre.
What is dyeing commonly used for?
- used to produce large quantities of coloured textiles
- single uniform colour
In what form can a textile be dyed?
Fibre, yarn or fabric
What is the definition of printing?
Printing is the application of colour to give definite designs or patterns
What is printing commonly used for?
-used industrially to create multiple copies of designs with various complexities in a range of colours.
What is the similarity between printing and dyeing?
-printing also involves localised dying or pigmentation in a way dictated by the design.
How are the printing and dyeing processes different?
- printing must be done with precision to ensure accurate repetition of copies
- printing can be applied to most textiles in a variety of forms
What are the 3 stages of printing?
- transfer
- fixation
- wash off
Describe transfer.
- dye is transported to the fibre surface
- the paste dries to form a surface of film containing the dye.
Describe fixation.
- movement of dye into the fibre interior itself (diffusion)
- aided by heat and/or steam to ensure rapid fixation
- dye-fibre interactions are formed
Describe wash off
- done with detergent and water
- removes excess paste, unfixed dyes, chemicals and thickener
There are two types of printing inks, what are they?
Paste inks
Liquid inks
What is viscosity?
Viscosity is the thickness or consistency of a liquid
What is the purpose of having appropriate viscosity in your mixture?
- it transfers the colour during print
- ensures the colour remains in position after transfer
What are three important factors if a viscosity formula?
- careful selection of ingredients
- ensuring appropriate quantities
- efficient mixing (homogeneous)
What does ‘pH’ represent?
The strength of acidity or alkalinity
What is the range of numbers in the pH scale?
1-14
1 being strong acid eg sulphuric
14 being strong alkali eg sodium hydroxide
7 is neutral
Name the 8 ingredients used in screen-printing paste.
- Dye or pigment
- Solvent (water)
- Solution assistants
- thickener
- Humectant
- Dye fixation chemicals
- Protective agents
- Miscellaneous
How are dyes applied?
- applied through water, usually soluble
- dyes transfer from the water and attach to the textile material
Dye is soluble in water. What is the name used to describe this property?
Substantivity
Describe the mechanics of how dyes fix to textiles.
- dyes diffuse inside the fibres
- intermolecular forces hold from between dye and fibre molecules to hold the dye in place
- in some cases with reactives, chemical bonds are formed
Describe the mechanics of how pigment attaches to textiles.
- attached using binders
- are attached only at the surface of the fibres as a coating
What are 7 important characteristics of a dye?
Hint: CPSDFCE
- colour
- physical form
- solubility
- diffusion
- fastness properties
- cost
- environmental considerations
Describe 3 things taken into consideration or the environment when dyeing.
Non-toxicity
- non-dusting behaviour
- residual colour
