Need Help Identifying These 2 Paper Types

@Rodgcam, can you send me a backlight comparison of a Washington-franklin 5c and a Pan american of yours so I can compare?

The Armstrong book, while still of value, was published 45 years ago, and has outdated information. The page you are referencing discusses China Clay paper; this paper variety was delisted in catalogs years ago.

But carry on with your research. New discoveries are always possible.

How about a scan (not a cell phone pic) of the back of your Pan-Am without any backlighting.

Gladly as requested a scan of the back of the Pan American stamp :

Thanks @Germania

I did read the Linn's article, it explains that the China clay paper stamps were delisted because research shows that the China Clay paper stamps are actually Bluish Paper stamps just with a minor variation so they are actually the same and that the china clay was not a deliberate experiment but a mistake where dirty water was used to make the bluish paper stamps.

You are correct the book is extremely old and there is a lot of newer information available from other sources.
There is also a lot of conflicting information out there, Robert Furman wrote a research paper saying that China clay papers are darker than the traditional bluish papers while Martin A Armstrong says they are lighter, it really is a difficult topic but what we can say for sure is that the Pan American stamps were printed in 1901 and were only printed on 100% wood pulp paper and they are not that far apart time/technology wise from the 1909 printings which is why it is such a good candidate to compare the perf 12 washington Franklin to.

another comparison, both washington-franklin perf 12 stamps, notice the "brown" glow of the 1c paper but the bluish stamp has a cooler white/gray glow to the paper. I just want to know if this is normal or not? If anyone has an example to show?

Asking 5 people in this group for an "expert opinion" will get you 10 non-expert comments. But I'll add a bit of information. The book, "The Papers and Gums of United States Postage Stamps, 1847-1909" from R.H. White has a section on Plate 19 for the 1895-1902, 1908 Issues. If you want a PDF copy (3 pages), then send me an email and I can get it to you. Here are a few screenshots:

Thank you @Parttime, this is brilliiant. From what I am reading 19-3 says that the 1908-1909 issue can be found on white paper. Is this white paper a heavily bleached wood pulp paper? 19-3 goes on to say "The porous soda paper is characteristically soft and is generally considered to provide a poor printing surface".

Let me add one of the "ten non-expert opinions". As I stated back a few posts and as pointed out in the reference material above, you are seeing the "pale amber gum" residue.

Interesting how the paper is white at the edges and watermark locations (as I said earlier). Why do you suppose that is? Two different paper types in one stamp? That would be a new one. Or could it be that the paper is much more dense from compression in those areas and not as prone to absorbing the gum?

Firstly, I would like to apologize for an all encompassing comment about non-experts on this forum. There are many non-experts giving their opinions here (like me), but there are some knowledgeable people adding well supported commentary. Thanks to you people for making this a better forum.



I didn't add some more information from the Plate 20 section. Here is something that may be of interest:

Thanks @Partime once again for the valuable information, I will send you my email. I would love to read through this material.

Based on the information you have given me I can say that the paper of the 5c Washington Frankiln is not soft or porous at all, the stamp feels very rigid and dense.

I have taken some pictures with my digital microscope however they are not brilliant, will see if I can get one that can provide better quality images, these are both taken from the "center" of the stamp next to the portrait where there was little ink to interfere with the photo :
This photo is of the 1c Green Washington-Franklin, you can clearly see the light spots as described in your post :


This photo is taken of the 5c, to me this looks a lot more dense with less light spots, also the fibers are a lot more dense and interwoven with less small broken fibers :