Before we venture any further, we must make very sure that we are all familiar with the concept of percentages. Basically, a percentage gives the number of parts per hundred that that component represents of everything together. So, 20% yellow in a mixed colour would mean that for every 100g of mixed colour, 20g would be yellow.

Percentage is calculated by firstly adding up all the components in the mix to obtain a total, secondly multiplying each component contribution over the total by 100.

 
     
 
WORKING EXAMPLE		  
     
  A colour comprises of 35g red, 45g yellow and 40g of white, the percentage formulation is calculate as follows:- Total = 35g + 45g + 40g = 120g  
     
 
  Percentage red in colour 35/120 x 100 = 29.17 %
  Percentage yellow in colour 45/120 x 100 = 37.50 %
  Percentage white in colour 40/120 x 100 = 33.33 %
 
     
  As all colourists will tell you, it is not very often that you have the correct colour at hand or that you achieve the correct colour first time when colour matching. It is usually a backward and forwards effort with a few sample print strikes that eventually results in the right colour being achieved.

What very few colourists realize is the implications of all the little bits of ink they use or lose during these colour strikes and cleaning processes. What is usually done is that the figures are added up and rounded off. This is obviously not correct as each time a colour is struck some of the mix is used on printing and a little is lost on the squeegee and screen. This means if you had started out with 100 g of an original sample, you might only have 95 g returning back to the scale to be adjusted again.

Most colourists tend to forget this ‘loss’ of printed colour and just carry on as if they have a full 100grams left to adjust.

The correct procedure is that the container weight must be recorded at the beginning of colour matching and be noted. When the sample colour is returned for adjusting, a new start weight for the mix left over must be recorded. This can be illustrated by the following simple example: -

  
     
 
  EXAMPLE
  Original sample weight
100.0 g
  Return weight
95.0 g
  Additional colour
1.9 g
 
     
 
  INCORRECT METHOD
  Original colour
100.0 g
  Additional colour
1.9 g
Total
101.9 g
 1,86 % in final formulation
 
     
 
  CORRECT METHOD
  Return weight
95.0 g
  Additional colour
1.9 g
 
Total
96.9g
 1,96 % in final formulation
 
     
 

This means that when production of say 10 kg of colour is made:-

INCORRECT METHOD
186.0 g
 of colour would be added
   
 
CORRECT METHOD
196.0 g
 of colour would be added

The colourist would have to readjust the production colour by adding the “additional” amount of 10 g of the “touch” colour that should have been added in the first place. This might not seem like a large difference at all, but it is extremely vexing when you have two or more “touch” colours in a formulation.

This problem is obviously compounded and made worse by the number of times the colour is struck and then adjusted. It would appear that the two colours are not the same at all - this is accentuated when the “touch” colour is a black, violet or cerise. This is the most singularly common mistake made by colourists when recording sample colours and passing on their recipes to the production staff.

We have devised an easy template to be use by colourists to avoid this particular problem and to help them to re-calculate exactly what is in the mix after adjusting the colour. Print a copy of the template.

  
     
     
     
 
 
 
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