BK Drying Time Recorder

10 Track Model (5 Pair Speed) - These have independently paired operating tracks. Separate needle carriers are moved from parked positions by depressing individual plungers, sliding them along to zero positions and releasing plungers when operative. At end of travel, needle carriers are in parked positions. Unless otherwise specified, the tracks operate at a speed of 12 hours. If required, provision can be made for some of the paired tracks to operate at speeds of 2, 3, 4, 6, 12, 24, or 48 hours. (Specify) The technique for preparing test strips and for reading the results is the same as for the standard BK Drying Recorder.

Determination of Drying Time - The drying time of alkyds, varnishes or paints is determined by adding the requisite drier and thinning to a viscosity at which the material is normally applied. The finish is allowed to stand at room temperature for 24 hours to "mature". A test strip measuring 12" x 1" (which may be of plain or ground glass or of other suitable material) is prepared by casting a film upon it by means of a special applicator which is accurately ground at one end to deposit a wet film thickness of 1.5 mils and 3 mils at the other. The test strips are placed on the table in their holders and the instrument is then operated as indicated below.

1. Select the required speed by turning the speed control knob in a clockwise direction and sliding in or pulling out to the required speed. Release knob.
2. Apply film to the test strips and place them on the Recorder.
3. Lift the release lever on the back of the needle carrier and slide it to the starting position.
4. Lower the needles on to the test strips.
5. Switch on and the needles will now commence the run along the strips. On reaching the end of the travel, the carrier automatically stops. Switch off.
6. Individual glass strips may be removed from the machine simply by depressing one end at the strip so that the opposite end tilts clear at the holder.

1. The first stage is a pear-shaped impression corresponding to the time taken for evaporation of solvent.
2. The second stage is the cutting of a continuous track, corresponding to a sol-gel transition.
3. The third stage is an interrupted track corresponding to the surface-dry time.
4. A fourth stage is where the needle no longer penetrates the film, corresponding to the final drying time.

A typical white enamel would have a drying time expressed as follows: 1-1/4 ----- 3-1/2 ----- 4 (hours)

The Applicator - is a 25 mm stainless steel cube with a hole drilled centrally from one face through to the opposite face. From each end of this hole a gap 12 mm wide is ground from the hole to one side of the applicator, thus providing 2 gaps per applicator. The applicator is placed at one end of the glass strip with the ground gap facing the end. Paint is poured into the hole and the applicator steadily drawn down the glass strip and off the other end, the gap being the trailing end of the applicator. Paint will flow through the gap depositing a 12 mm wide film on the glass strip.

The standard applicator has a gap depth of 75 microns (3 mils) one end and 150 microns (6 mils) the other, which will apply a paint film thickness of approximately half the gap size. Any gap depth between 10 and 650 microns can be supplied to suit customer requirements.

The Casterguide - is a device for simplifying and “tidying-up” the process of applying the paint film to the glass strip. It consists of a cast aluminum trough with a ledge on each side to carry the glass strip and a step one end to allow the user to hold the strip in place. The applicator is then posotioned on the glass stirp at the step end and filled with paint as described above. When using the applicator the casterguide ensures that the film is applied centrally and, as the applicator is drawn off the end of the glass strip, the surplus paint is collected in the trough underneath.

This operation may be repeated several times before cleaning is necessary. For this purpose use only suitable solvents, do not use caustic alkali or caustic detergents since these will attack the aluminum metal.