Zeasor,
I have a few notes for you about your comments and questions.
A sheet of coated paper is a little more than coated. It isn’t like cinderblocks which have stucco applied to the surface. Kaolin is applied in the process of making paper near the finishing so the clay is actually in the paper and not just on top.
A lot of post cards are printed on what is referred to as “C1S” or stock coated one side. This is done on reply mail so that the backside can still be written on with most pens and pencils.
With regard to detecting the difference between plain coated paper and one with a top coat;
NORMALLY, paper which is not coated with a finish will have a faint to strong smell from the ink which usually will be similar to the smell of a fresh newspaper. It stinks because of the oil based ink most printers use. (When we recycle ink the recycler takes the drums to a block plant where the oils are extracted from the pigments and the oil is blended and used to fire the block plants furnace. The pigment is bricked into solids which are sent to ink makers which supply the news trade. Typically one 50 gallon drum will yield one brick of pigment the size of a large fire brick. All the colors we use can’t be extracted of course so it is basically black. Like most recycling, the pigment goes to a cheaper product.)
Printing varnish and Aqueous based coatings are similar to one another and provides the characteristics of being able to both add gloss, semi-gloss or dull finish for effect and having a piece which can be processed almost immediately because the inked surface is buffered against contact with a second press run (as in turning the sheet over and printing on the back) or sending to be folded or cut.
A quick hint on a sheet coated would be where the piece is spot coated or reverse spot coated. An example of this would be a magazine insert were the product is glossy and the surrounding area is dull or a different appearance.
Sometimes it can be difficult in our shop to tell by appearance if a sheet is coated if the edges have already been trimmed. (aside from asking the pressroom or looking on the job record)
Not a certain test is trying to write on it with most gel ink pens. Most of them won’t dry on aqueous coating for several minutes if ever.
Aqueous coatings are water based (and usually ammonia solventized). When dry it usually has a slightly acrid smell.
Varnish is the older method still used by some printers. It is similar in base to the inks themselves, just no pigment. Varnish will be like any petrol based finish in smell.
Uv or ultraviolet coatings are the very slick coatings and a good coating will cause water to stand on the surface. Most cured Uv’s will have an almost sweet smell.
Another test is the fingernail or knife edge test. When scraped many Uv’s will loosen and lift in flakes from the surface.
With regard to plastic, look at your good grade of playing cards. These are almost always top laminated with a layer of plastic. This is a very thin sheet of film laminated on top so this is not technically a printing item and rather a finishing process since it is not applied as a printing method. There are more and more uses of these films on pieces which are designed to be handled a lot. Gift cards, prepaid calling cards, customer loyalty cards and key tags, insert cards like membership cards and credit cards which are glued onto offers for service are often coated with plastic. These can generally be distinguished from plastic solids such as real credit cards and the like.
Now a sidebar if I may.
There is a plastic sheet increasing in popularity which is a polymer (polypropylene).
We do print on this some for limited uses. Our first customer using this was a window manufacturer which needed insert sheets to go with window sets which would withstand outdoor conditions including inclement weather, freezing temperatures, extended exposure to sunlight. Instructions to the installer was printed on these inserts.
We chose this as a natural stock to use for our local BSA Council’s reservation maps.
At over 16, 000 acres and 100 miles of trails the reservation’s map has to be updated on a regular basis to be accurate for year-round use which means holding up in all sorts or weather and punishing conditions without the ink running or fading. (parts of the reservation are used year round)
This stock does this with only one failing, after repeated tight folding it begins to tear.
Many Scouts and leaders precut the map and tape them back together for sectioned folding (slightly larger than a USGS quad, it covers parts of 3 counties).
I mention this (one to put a plug in for BSA and the Reservation) because many in the forum, I know, have cross interests which may make this type of paper useful aside from honing. The paper is useful for other uses which include art and inkjet printing.
I have gotten some in packs under the National Geographic label for printing out maps on. Look up Yupo in your search engine for more information.
If you’re a Scout, Scout leader, parent of a Scout or have fond memories of being a Scout lookup the camps under,
http://www.bsa-brmc.org/camp.htm
Of particular interest to this forums members are the Mountain Man Outpost and Voyageur Trek which go to skills of the 18th century explorers and long-hunters.
The Council also has a 4500 acre aquatics base on the other side of the New River just down the road also detailed on the site.
The Council operates what Boys Life magazine staff calls “ The Philmont of the East”.
OK, I know that wasn’t knife related exactly but I had to offer it up.
About offset printing plates; some are thicker than others. That being said, none are very thick and have uses which aren’t much towards structure or strength. If cut they will have a sharp microscopic ragged edge. They have a multitude of uses though. If folded they tend to break if scored tightly. Think of them as super heavy-duty tin foil. (I wouldn’t cook on one though, the chemicals used to treat them for ink carrying is not nice for human consumption.)
On press blankets
I have used blankets to make:
Gaskets
Cleaning mattes
Shooting mattes
Cutting mattes
Axe and cutting head covers
Non-scratch watch repair mattes (excels for laying a watch face down while changing the battery and not damaging the crystal)
Non-slip pads of many types
Turn them over, canvas side up, to make a bottom cover for sharpening stones and diamond coated steels.
The canvas back can be suitable for making a heavy sharpening strop using paste.
(depends on the quality of the blanket)
100’s of other uses (like putting it under a gas can for transport and filling the push mower to catch spills.)
Small press blankets will be about 11” by 15” on up to 60” by 70” on a very large sheet fed press. (most of those are used for printing food can labels and the like)
The most common will be the small ones and medium format presses. These will vary by press but somewhere between 20 by 26 to 30 by 40 for larger presses.
*As I said before, an offering won’t hurt and I suggest asking up front, “ what would you charge me for a busted press blanket? ” Sometimes my answer is a blank stare followed by, “hang out a second let me see what’s in the back” while I look for a decent piece, gratis. Sometimes there isn’t any at the moment and I’ll just take a number or say come back in a day or three. (My policy and experience says “pay it forward”. If they don’t pay it forward it’s their loss. *”Your mileage may vary”, as the old disclaimer goes.)
Finally one last note for full disclosure. Kaolin clays, which much of this subject centers around, may contain trace amounts of radioactive thorium or uranium. While the amounts are small, truckloads of skidded stock can set off radiation sensors at weigh-stations and inspection points. This is probably not significant since the same materials are used for structured sharpening rods.
Happy experimenting and safe sharpening to all.
Anyone want to make a lite-weight aluminum sheath with some sort of protective liner? The rubber blanket might make an ideal non-skid mat for my stones. I am off to visit my local small printer this morning. I have several things to mooch. 