through the vat 12 and also to filter the fluid in the vat 12 a pipe 170 is in fluid communication with the vat 12 such that fluid may flow out of the vat 12 when a suitable valve 175 is opened fluid is drawn out of the vat 12 by pump 166 and passes through filter 168 before flowing back into the vat 12 through line 164 if desired valves 172 and 174 may be provided to allow for the vat 12 to be drained either before or after passing the fluid through filter 168 after the books 72 have been exposed to the treating medium for a predetermined period of time effective for deacidifying the book they are dried the dryer may be a separate unit or a separate section within an interconnected system or may be part of the vat 12 in the latter embodiment the treating fluid would be drained from the vat and transferred to a holding tank not shown warm air may be piped into vat 12 as described below for dryer 140 turning to fig6 7 a separate dryer 140 is shown it includes a rack 180 made of flexible meshed webbing 142 secured to rods 144 the webbing drapes loosely between adjacent rods each rod 144 is attached to the.