Whatever Became Of China Clay Paper

Found this on an earlier thread on this subject:

"Scott specialized de-listed the China Clay stamps. I feel for all those who owned the purported China Clay paper stamps. THey were a little pricey.
Does any one have any updates on the status of the China clay stamps.
The bluish paper stamps are not the same as the stamps which were formerly listed as the China Clays."

The thread ended without an answer to the question.

Knowing that China Clay Paper was just a myth and has nothing to do with Bluish paper has me wondering what exactly was being misidentified as China Clay Paper. Was it a type of paper you could identify by sight, or did it look like normal stamp paper but feel different? Having never seen one I'm wondering if this 6 cent Washington is printed on the mythical China Clay Paper:






The smaller of the two 6 cent Washington stamps perfs 12 on all four sides. The larger perf 11 on all four sides. The papers are distinctly different in appearance and feel. The paper of the smaller stamp is thicker to the touch and shades darker. Again, I know China Clay Paper really doesn't exist but before it was delisted in Scott collectors used some type of criteria for identification. Does anyone have knowledge of the history of this myth they'd be willing to share?

As I understand it, China clay paper wasn't actually an experimental paper with clay content, as people thought before, but rather a batch of regular 35% rag paper that was for whatever reason just dirtier. Careful chemical analysis of "China clay" paper didn't show the makeup people assumed, and indeed more importantly didn't distinguish it from non-"China clay" rag paper. So, not a real variety, even if it looked like one a hundred years ago.

John Hotchner had an article in Linn's about it a little while ago, with a couple other examples of dubious varieties: https://www.linns.com/news/us-stamp...t-exist.html

Now, would your stamp have been expertised as "China clay" back in the day when people thought that was a thing? Who knows? Apparently paper color was the main determinant, if your stamp had the right shade of gray-blue it was good. Comparing color on a computer monitor is tough, so I'm not sure if your stamp has the right hue.

The more important thing is that it will not be certified as "China clay" today.

AJ Valente will hopefully weigh in on this since he "wrote the book".

Askphil contributions:
Art paper: superfine calendered paper with a china clay surface, or kaolin, giving it a enameled finish for the printing of
half-tone blocks.

China Clay Paper: paper with a high mineral content used for the US Washington-Franklin stamps, 1908-09.

There was a series of excellent articles, combined with scientific analysis which disproved the existence of China Clay papers in the W-F series. This was published over the last couple of years in the United States Stamp Specialist.

The former China clay paper stamps are now classified as "dirty water" paper because silica in the water became embedded in paper produced during drought conditions when the mill pond was low. The paper is often dark in appearance. Unlike bluish paper, watermarks do not show clearly in back light. Originally, the variety was applied to paper lighter in appearance with some characteristics suggesting that kaolin was added. Later the definition was hijacked to describe the muddy water paper. I don't know if the "original" china clay paper was ever tested. I have some dirty water stamps Tested by the late Ted Liston.

Thank you all for your information. Appearance of the paper was the criteria for identification. Paper types used for stamps is a specialty in itself. Dirty water paper is a term I haven't heard before and I will add it to my list of things to learn more about. There aren't many collectors out there who have a grasp of this aspect of the hobby as well as all of you. You are an elite group. Thank you again for your contributions to this thread.

Hello, is it still today correct that the dirty paper from Nov. 1908 and the gray paper from Dec. 1908 are no real paper varieties (no experimental papers)?

And: what is the difference between the bluish paper and the former so called China Clay if both are gray, have high rag content and black specks? Just the look, as bluish paper is darker, more cloudy mesh, the watermark better to see before light?

The two are not actually two but one and the same with the so-called China Clay being a minor variation of "blue paper". These minor differences are endemic to catalog's and do a disservice to collectors when you consider how papers and inks were manufactured at the time. We are not talking computer controlled ASTM guided processes here. Listing them DOES make sellers more money however.

PS:

Mystic still has this in their catalog:

But did then any of the China Clay stamps have then been certified as bluish paper?

I thought that the China Clay has now been defined as dirty paper (from silt) with some rag content and black specks. The gray paper tough has no black specks and is neither the old China Clay paper nor the Bluish paper.

This is why I asked if there has been any recent research and what has become of:
- China Clay paper (> Dirty paper)
- Gray Paper

Probably still not a real paper variety?
I think Gray paper could be interesting to look for.
(not talking about bluish paper)

I haven't had a chance to digest it, but the June 2025 issue of The United States Specialist has a 14-page article "The Coming and Going of China Clay in BEP Printing Paper: Kaolin Content in the 2c Stamps of the First, Second, Third, and fourth Bureau Issues" by Harry G. Brittain, PhD.
For instance, Figure 1's caption: 'XRD patterns of cellulose and of cellulose that had been spiked with approximately 10% of kaolin (i.e., white or "China clay").'
Also included are several graphs that plot %Kaolin content by plate number range, and by year range (for the various stamp series, respectively).

Hi @StampsOnMail, I read the paper you are talking about, according to the research paper titled "Researching a Rarity:The "China Clay Papers' By Robert Furman Part II", the China Clay experimental paper stamps of 1909 do not contain significant amounts of Kaolin.

I would like to know from the community, as the China Clay experimental paper stamps of 1909 are no longer in the catalogue and are now basically categorized as bluish papers does that make any research done about the china clay vs bluish papers invalid or no longer acceptable by the stamp community?