NOVELTY - Testing coating formulations comprises: providing many coating formulations; dip coating many test substrates in the coating formulations to generate many coated substrates; generating a variation between at least two of the coated substrates; characterizing the coated substrates to obtain characterizing results; and selecting a subset of many of the coating formulations based on the characterizing of the coated substrates.    USE - The methods are useful for testing coating formulations and sol-gel coating formulations (claimed), where the coating formulations are useful in manufacturing semiconductor device, solar cell, glass or energy cell.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) testing sol-gel coating formulations comprising: performing a first screening to identify a subset of sol-gel coating formulations having predetermined characteristics, where the first screening comprises providing many sol-gel coating formulations within a housing of a coating formulation apparatus; dip coating many test substrates in many of the sol-gel coating formulations to generate many coated substrates; generating a variation between at least two of the coated substrates; and selecting a subset of the sol-gel coating formulations based on characterization results; and performing a second screening (104) by coating a second type of many of the test substrates with the selected subset of the sol-gel coating formulations, where the coating is performed using spin coating; and    (2) an apparatus for testing coating formulations comprising: a housing enclosing a testing chamber; many vessels coupled to the housing and positioned within the testing chamber, where each of the vessels is configured to hold one of the coating formulations; a dip coating assembly coupled to the housing and configured to (a) hold many test substrates, (b) simultaneously dip each of the test substrates into one of the coating formulations, and (c) draw the test substrates from the coating formulations to form many coated substrates; and a variation generating system coupled to the housing and configured to generate a variation between at least two of the coated substrates.    DESCRIPTION OF DRAWING(S) - The figure shows a diagram of a combinatorial funnel for screening materials.    Primary screening (102)    Secondary screening (104)    Tertiary screening (106)    Device qualification stage (108)    Manufacturing stage (110)