Task 5: PAPERMAKING
Sample sheets of paper made in the laboratory are known as handsheets. They are made using a standard device known as a handsheet mould. The process of making paper involves the following steps:
1. Dilution of fibers with water
2. Drainage and formation of a wet sheet on a wire mesh
3. “Couching” (pronounced COO-CHING) transfers the wet sheet of paper on the wire mesh to a dryer surface, such as a blotter or paper towels.
4. Pressing to remove more water and bring the fibers into intimate contact.
5. Drying to remove even more water to strengthen the bonds between the fibers.
One of the most critical attributes of a manufactured sheet of paper is its “heaviness” or the amount of fiber that is in the sheet of
paper per unit area. The term for heaviness is “basis weight,” which is expressed
basis weight = grams of dry fiber__________
square meter of paper surface (one side)
Since the sheet mould is six inches in diameter, the corresponding surface area of the sheets made is 0.02 m2
The target basis weight for this activity is 100 g/m2. The amount of dry fiber required is determined as follows
grams OD fiber = (100 g/m2) x (0.02 m2)
= 2 g
Since the slurry consistency after mixing is to be 1%, then the amount of slurry to mass out for each handsheet is
Grams slurry = 2 grams OD fiber
(1% consistency)
= 200 g
1. Screw the top part of the handsheet mould onto the lower part only until slightly tight. If too much force is used, then it will be very difficult to separate the two parts after making the handsheet. If the two parts are not secured tight enough, the papermaking slurry will leak out.
2. Measure out 200 g of your slurry.
3. Measure 4 inches below the rim of the top part of the handsheet mould. Using a permanent marker, draw a line at this point. This will be the fill-line for each handsheet you make.
4. Fill the mould with tap water until about halfway full.
5. Pour the slurry into the mould. Fill with tap water until the level reaches the marked fill-line.
6. Agitate the mixture in the mould with and up-and-down action rather that a swirling action. Using a large graduated cylinder works well. Use the same technique for all handsheets.
7. Remove the agitating device, wait for 5 seconds, and then remove the stopper or the other device at the bottom of the mould.
8. Hold the mould steady and level until no more water is seen draining from the bottom hole. Carefully unscrew the mould to separate the top and bottom sections. Tilt the bottom section from side to side to allow edge water to drain off in all directions.
9. The challenge is now to transfer the fragile wet sheet from the forming wire to another surface so that it can be pressed and dried. Set the bottom mould section on a steady surface. Place three paper towels together, then gently lay the combined towels on top of the wet paper sheet on wire.
10. Use a kitchen rolling pin to gently roll the paper towels down onto the wet paper sheet, using no pressure on the pin. Do five back-and-forth rolls.
11. Remove the two top paper towels, which will now be saturated with water. Replace them with two dry towels and repeat the rolling pin technique. Continue this process until no more water can be removed from the sheet.
12. Lift up the bottom paper towel and see if the sheet will follow it up (“couch” off of the towel). If so, continue lifting with a smooth, continuous action until the sheet is transferred to and is lying upon the paper towel. If not, it may be necessary to pinch one edge of the sheet edge and clamp it to the paper towel, then peel up the resulting sandwich to transfer the sheet to the towel.
13. Place the wet paper towel, with the wet paper sheet on top, on a flat, heat-resistant surface covered by three paper towels.
14. Have the iron set on the highest setting, but do not engage the steaming mechanism. Place three paper towels on top of the wet paper sheet. Place the iron onto the paper towels and press down firmly, moving the iron gently across all of the area covering the wet sheet. Co this until the sheet has been heated thoroughly (2-3 minutes) – this may take some trial and error. Remove the iron, allowing the heated water to evaporate as steam. Repeat this procedure until the sheet is dry. NOTE: once a workable procedure has been established, it should be used for all experiments.
15. Carefully peel away the dried paper sheet from the paper towels on each side. Use a pencil to lightly mark the sheet with some sort of code or identification label.
1. Referring to the handout “ The Chemistry of Making Paper,” illustrate why cellulose fibers are hydrophilic.
2. Referring to the handout “ The Chemistry of Making Paper,” explain and illustrate why one needs to press and dry a wet sheet of paper after it has been “couched” from the wire mask rather that being allowed to air dry.