It has been observed that ALUMINA HYDRATE improves the finish of dried ink films. If gloss varnish can be used, the addition of same increases the finish still further. A combination of hydrate and gloss varnish is frequently used

Because the ALUMINA HYDRATE has acidic properties, it does not change appreciably the acidity of the lithographic fountain solution during the printing operation. The hydrate is therefore a useful ingredient in lithographic inks.

In multicolour printing where inks trap over each other, it is obviously an advantage to have transparent inks after the first one. ALUMINA HYDRATE qualifies very well as a transparent extender when an ink needs to be reduced in colour strength for multicolour printing

The majority of the moisture-set inks (often called steam-set inks) contain a resin that is very acidic in nature. This resin is a fumarated resin and has an acid value that is over 300.

In a number of inks, a blend of clay and ALUMINA HYDRATE can be used as the extender to arrive at a low cost and acceptable printing qualities. However, if the printing run be a long one, it is safer to select a good printing extender to prevent piling on the rollers and on the printing plates.

More present day pigments are faded or changed in hue by alkaline substances than by acidic ones. The majority of the Triphenylmethane and Diphenylmethane pigments, such as Methyl Violet and Alkali Blue, shift their chemical structures to the colourless state when alkali is present.

The popular Iron Ferrocyanide Blues readily fade with alkalies. The use of ALUMINA HYDRATE , is a safeguard in cases where alkaline materials can be activated by the presence of sufficient moisture that can yield fading of sensitive pigments.

1512 ALUMINA HYDRATE has a reduced reactivity. An accelerated test can be conducted of the ink at 160 o F during three days to examine the possibility of livering, either on storage or during hot milling.