dispersant in the amounts set out in table 1 the resulting dough was extruded using a commercially available basket extruder obtainable form e g russell finex ltd to produce 2 mm diameter granules table 1 also sets out the results of the tests conducted on those granules the 2 mm extruded iron oxide granules produced on the basket extruder displayed good strength and flow properties but gave poor dispersion test results of well over the 50 level the latter problem was illustrated by a brick made with the red granules showing a large colour shift compared to the powder control brick with the delta e well over the expected 2 limit red spots were also visible in the brick a series of experiments were performed to optimise extruded granules of iron oxide pigments for their end use dispersion property the same test rig as used in example 1 was set up but using a perforated plate with 3 mm holes pigment paste was compressed through the holes using a hand roller with the extruded granules being collected in a tray beneath the perforated plate these extruded granules were then dried in a laboratory oven iron oxide powder yellow iron oxide yb3100 red iron oxide rb2500 black iron oxide bk5500 were mixed with soda ash to adjust ph water and the following dispersants and wetting agents were used to form the extrusion dough in amounts set out in table 2 dispersants dispex n40 dis suparex dp ccoo2 sup narlex ld3 1 nar wetting agents ethylan bcp et1 surfinol 104 s sur arylan sy30 ary ethylan bcd 42 et2 lankropol k02 lan the granules were subjected to drop tests and dispersion tests and the results are given in table 2 3 and 4.