7 vs 10 mill mylar for Vandercook

The top sheet that we have on our Vandercooks is 7 mill mylar. I notice that Talas has rolls of both the 7 mill and 10 mill mylar.

Although I don’t see any impact on printing quality the 7 mill will show indents when we’ve run a particularly large edition.

I was wondering if anyone had an opinion that the 10 mill might be better to use.

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Eric Holub
15 years ago

I use .010 acetate as topsheet on my Vandercook 325, which has a retaining bar on an overhand reel. In addition to a careful score with a burnisher to define the bend, I also put Permacel cloth tape on the hem so the clamp has a better grip.
But on my Heidelberg cylinder I use .004 acetate topsheet. This has a more standard underhand reel (so did my SP-20). Printers did not need to tape the tail to the reel with these. All you need to do is pull the tail taut under the reel and fold it up over each edge, preforming the tail. Then start at the outmost fold, and turn the reel and tail until the pawl can be tightened. With plastic as opposed to tympan, you will have to keep turning until the tail pulls against itself and catches.
Another possibility for reel design is the split reel on some later model Vandercooks. Either thickness might work there, but I have had the .010 acetate tear as it was tightened unless it is very carefully trimmed and folded.
Mylar is preferable to acetate, but acetate is cheaper and available on 40″ rolls at my local art supply store.

Paul Moxon, Moderator
15 years ago

Nicholas cut the drawsheet taper so it came to a point. He aligned the point to a center line drawn on the reel rod, placed a single magnet on top of the mylar and wound the taper around the reel rod. The side-to-side play built into the reel rod is designed to eliminate any unevenness regardless of the drawsheet material.

Rare-earth magnets are stronger than ferrite magnets, thus a smaller one can be used than what might be expected. Be sure to choose a size that has enough height about a 1/4″ so that you can pry it free with you fingers.

Paul Moxon, Moderator
15 years ago

I prefer 7 mil, because 10 mil is more difficult to score and fold. The greater thickness also makes it more difficult to wind the tail around the reel rod.

On a related note, if a press does not have a reel rod clamp bar most printers use adhesive tape to hold the tail end to the reel rod. A better solution is to use a rare earth magnet. This idea was shown to me by Nicholas Kennedy at Trip/Print Press in Toronto.

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