HANDSHEET MAKING PROCESS

HANDSHEET MAKING PROCESS

3.5.1    Stock Preparation

            15 g (o.d.) of pulp was weighed and transferred to the disintegrator shown in figure 3.7. 1250 ml water was added to give the consistency of the pulp stock at 1.2 %. Then, the pulp stock was disintegrated for 2000 revolutions.

Figure 3.7: Disintegrator.

            After the disintegration, the pulp stock was transferred to the plastic pail. The disintegrator was rinsed with 1000 ml water and added to the plastic pail. Extra water was added into the pail to dilute the pulp stock to 0.3 %.

3.5.2    Freeness Determination

             CSF freeness tester was thoroughly cleaned with distilled water. The drainage chamber was placed on the upper supporting bracket with its lower lid closed and the upper lid and air-cock opened. The graduate cylinder was placed in position to receive the discharge from the side orifice whereas the 500 ml beaker was placed to collect the discharge from the bottom orifice. A blank test was first carried out using distilled water.

            After that, the pulp stock from the plastic pail was stirred thoroughly to ensure a homogeneous mix and its temperature was taken. 1000 ml of pulp stock was measured accurately using a 1000 ml graduated cylinder. The pulp stock in the graduate cylinder was mixed by closing the top of the cylinder with the hand and inverted the cylinder 180° three times gently. Figure 3.8 below shows the CSF freeness tester used.

            Figure 3.8: CSF Freeness Tester.

            The pulp stock was poured gently but rapidly as possible into the chamber. The top lid and the air-cock were closed. The bottom lid was opened. After 5 seconds from the time the addition of the pulp stock was complete, the air-cock was opened fully in a single motion. When the side discharge has ceased, the volume discharge from the side orifice was recorded. The corrected CSF freeness at 20 °C and 0.3 % consistency was calculated.

3.5.3    Stock Consistency Determination

            The screen and the cylinder of the handsheet machine ware cleaned. Then, the cylinder was locked tightly. The pulp stock from the plastic pail was stirred thoroughly. 400 ml of the pulp stock was measured using graduate cylinder. The pulp stock was poured into the handsheet cylinder and the start button was turned on. At the same time, the graduate cylinder was rinsed with water and it was poured into the handsheet cylinder.

            The air bubble was released into the handsheet cylinder by the handsheet machine automatically. The water was drained out of the handsheet cylinder and the wet handsheet was formed on the screen. Then, the handsheet cylinder was unlocked and pushed behind. Two pieces of the blotter papers were put centrally on the wet handsheet.

            Then the couch plate was laid centrally on the blotter. The couch roll was placed gently on the middle of the couch plate. The couch roll was rotated backward and forward to perform the five complete rolls. The couch roll was lifted. The wet handsheet was removed with blotters and couch plate from the wire together in a manner similar to that of opening the cover of a book. After that, the wet handsheet with attached blotter was removed from the other blotter and couch plate.

            The wet handsheet was dried by placing the wet handsheet with attached blotter (wet handsheet side up) on the hot plate. A fresh blotter was put on the top of the wet handsheet. The stake was pressed with the hot iron.

            Then, the dry handsheet was pulled from the blotters. The handsheet was cooled down in the desiccators for 10 minutes. The dry handsheet was placed in the closed balance and the weight was measured immediately. Then, the consistency of the pulp stock was calculated.

3.5.4    Handsheet Making

            Based on the calculated pulp stock consistency, the required volume of the pulp stock to produce a handsheet with 60 grammage (60 g/m²) was calculated. The required pulp stock was measured. The handsheet was made by following the instruction from section 3.5.3 without drying step. Figure 3.9 below shows the handsheet machine used in laboratory.

Figure 3.9: Handsheet Machine.

            The wet handsheet and attached blotter (wet handsheet side up) was placed on a fresh blotter and located centrally on the plate using press template. The wet handsheet was covered with another plate and one fresh plate. The steps above were repeated for 7 handsheets.