This paper focuses on the construction of D- and Ds-optimal designs for a secondorder
response surface model when the block sizes are not fixed. Overviews of the Procedure
OPTEX in SAS for the construction of these designs are given. With the BLOCK statement this
procedure can produce optimal designs when the block sizes are fixed but for unknown block sizes
it requires additional programming to generate the optimal designs for a given number of runs and
number of blocks (see Atkinson, Donev and Tobias, 2007). An example about a pastry dough experiment
(Goos and Jones, 2011) is used to demonstrate how to generate designs in such situations.