A Costly Mistake - Tony Clark

A Costly Mistake
(Tony Clark)
Some months ago a Director of a Bindery sent me a book that the Publisher had rejected due to pages falling out. He asked me to strength test the book and refute the claim which if proven would cost him some £50,000 to re-print.
The tests showed that the centre pages were very weak and the best result was 2N/cm. After taking off the cover of the spine it could be seen that the cover adhesion was less than 50% and there were large holes in the glue film.
When I telephoned the owner of the Bindery he said that was impossible as the binding machine was computer set. I informed him that the computer cannot see holes in the glue film, (neither can the operators) unless they remove the cover and cut down the spine for a good inspection.
Every time the machine is changed for different sizes or after the spine cutter has been sharpened the books must be checked. Changing the adhesive from one make to another can mean different settings due to a viscosity change and even the ambient temperature can make a difference.
What about moving from 8 page sections to 96 page units or from perfect binding to burst/slotted binding? (See the box )
That of course is the one change-over when the binding machine has to have most of its settings altered.
When setting up a machine to perform the burst-binding operation, firstly, set the infeed table so that the sections do not touch the spine cutter. The bookblock then has to be moved over the glue rollers to make sure that the spine clears the rollers otherwise the folds pressed on to the first roller would close the burst or slot preventing adhesive penetration.
With burst-binding the adhesive is only pushed into the centre sections at the cover- application station. The adhesive should be still movable as it presses the cover or the lining materials upwards and the side nips.
One other point, when the slots are being cut and the last fold has been made do inspect the sections because the fold generally is not perfectly down the centre of the fold and the slots are sometimes to one side or the other.
Therefore to get adhesive into the first or last section a wire needs to be placed on the first roller to create a bow wave of adhesive to help the application into that off-set fold.
When the first burst-bound books have cooled open the first and last sections in the middle to make sure that you have got good adhesive penetration.
It is generally the first and last sections that fail in slotted/burst binding. If ever the centre sections fail it is always due to lack of spine upward pressure for when the adhesive is pushed into the slots the side nip moves it just that little bit more.
Now that you have completed the burst bound job the whole machine has to be re-set for Perfect binding. Measure the amount of fold cut off and the gap between the first glue roller and the cut spine before re-setting the height of the cover station.
So, to go back to the faulty book sent to me .If the operator had done the standard test of removing the cover or putting the book on a simple page pull tester the Bookbinding Company in question would not have had to pay out for a reprint and bind.
All operators should have a magnifying glass and a knife to check the glue film. ( If you use too much glue you are throwing away money and too little and the books will fall to bits or will not have the cold/heat resistance). All larger Binderies should have a page strength tester; these units once purchased will last a life time of service as there are no parts to wear out and the digital readout runs from the mains or a re-chargeable battery. The cost of reprinting and binding may be off set with insurance ( but these costs keep rising ) and it is the loss of reputation that cannot be brought back. Always test books at the beginning of the run and at regular intervals throughout. Tony Clark 28 5 07

Burst / slotted binding
Burst, slotted or perforated binding is a system whereby a slit or a slot is punched into the paper prior to the last fold. The length of this slit will be governed by several factors:
1) The type of adhesive used.
2) The speed of the binding machine.
3) How clean a cut can be made by the folding machine or web press.
Burst / slotted binding has been extremely successful with emulsion adhesives. This is because after the book block is bound, emulsion will carry on moving until completely dry. Other adhesive systems suitable for burst or slotted binding include the Twinflex or emulsion – hotmelt system, provided that after the emulsion has been forced into the slot, the surface adhesive is scraped off and brushed out and sufficient heat is used to dry all the emulsion before the hotmelt is applied to the spine. Two-shot hotmelt systems are also in use with burst binding, using a primer hotmelt of very low-viscosity and long open-time and a higher-viscosity hotmelt that helps to force the primer product well into the slot.