View Full Version : "Cockle" finish paper- ? for Catboat
10-12-2008, 08:08 AM
Mr. Catboat (or anyone else who knows)-
I wonder about the "cockle" finish used on some of the onionskin papers, supposedly to make them easier to erase on. Is this indicative of more abrasives, or is it just a particular texture the paper has? The specific paper I am using is Southworth 9 lb. onionskin, 100% cotton, cockle finish.
Thanks very much, take care!
10-12-2008, 04:31 PM
Cockle finish is a weird one. Weird in that, to a papermaker, it's an undersirable characteristic of the paper.
"Cockle" means the sheet has many "puckers" on in. If you look at the sheet's surface from low angle, you will likely see a non-smooth surface. Cockles or puckers vary in size, but they are area of paper about 1/2" to 1" in size. Some pucker up, and some pucker down. It is due to non-uniform water release (drainage) from the paper. Then as the sheet passes continuously through to the dryer section of the papermachine, the areas of the sheet which have released water at different rates has presented a sheet that will dry at various rates. You use low levels of "draw" or paper tension (which allows the sheet to pucker). The dryer sections of paper (can be areas of 1/2" to 2" in size) will dry faster than the wetter sections (same ~ size area). The uneven degree of heat to the sheet causes the fiber bundles (areas of fiber) to shrink at different and non-uniform rates. This results in a "pucker" or "cockle." When you WANT cockles, is if a customer wants a sheet of paper that is to look like a "hand made" sheet of paper (like from 100+ years ago), and then the sheet was air dried (no tension).
If you want to eliminate cockles or puckering, the papermaker increases the tension of the sheet, at various points along the machine. Today's papermachines make then sheet nice and smooth, almost like ironing it. A smooth sheet is better for printing (better transfer of inks). But, if someone wants a "cockle finish", the papermaker will reduce draw / tension to the sheet, and make the stuff.
It's sort of like having non-uniform areas of corrugation (corrugation would be more linear lines, where as cockling or puckers are "circular" corrugation. By corrugation, I mean the sheet's high and low area create a space. If you stack a bunch of sheets of paper that has cockled, compared to a stack of sheets that does not have cockles, the cockled stack will be bulkier (due to the high/low voids made from the non-uniform drying).
From a paper patching stand point, it shouldn't make any difference, good or bad, for wrapping a bullet. It may make it dry a bit non-uniformly, as that is what caused it in the first place (some wraps may be tighter or looser due to fiber drying characteristics). That's a guess, and it may be miniscule, or non-existant.
I wouldn't go out to BUY cockle-finished paper, as it is just bond grade paper (good fiber, and good quality), but with that funky non-uniform fiber drying issue. Certainly don't pay any PREMIUM for it. It still has a fair amount of filler to it (probably at least 12-15% inorganic filler (clay or calcium carbonate), and may be as high as 20%+ filler.
I still like tracing paper or lens paper as a bullet wrap paper. Low ash, strong fiber.
But, as I always repeat... "if it works for you, then use it."
10-14-2008, 12:24 AM
..............Some of the last 9lb paper (25% cotton) I had was of "Cockle Finish" . The texture was very even and it had a pleasant crinkle to it when handled. I figured they ran the paper between some textured rollers or something to form the texture.
10-14-2008, 12:21 PM
....it had a pleasant crinkle to it when handled.
That should warm the cockles of your heart...
10-14-2008, 07:38 PM
Thanks for the very informative reply, Catboat. The cockle finish is not something I'm seeking out, just something that I've come across as I constantly search for suitable paper. I wasn't sure if the finish was a mechanical effect or a chemical coating. I don't want to wear the bore prematurely if the finish is highly abrasive.
Again, my thanks! Take care,
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