ID'ing Mexico 251/286

[youpiao]

Mexico, Scott Nr 251 was watermarked. However the watermark screen was too small for the sheet of stamps and 1 column in a sheet will be unwatermarked.

Scott Nr 286 was unwatermarked, and in almost every other way, identical to 251. The difference, as mentioned in Scott is that the paper on 251 has a vertical grain or mesh, and 286 has a horizontal grain or mesh.

Can anyone detect the grain direction in any of these scans? It's hard for me to discern if I am seeing a horizontal grain, or just the impressions from the recess printing.

One test for detecting the grain is to soak the stamp and see which curls first, the sides (V grain) or the top and bottom (H grain). Guess what? 2 corners curled first, diagonally, on mine.

[khj]

First a pre-warning: some philatelists don't use the same definition of "direction" as paper-manufacturers. In particular, I have seen on some stamp sites that they use mesh direction and grain direction interchangeably -- but they are not the same thing! Since Tedski stated "grain direction", we will stick to "grain direction" and ignore mesh configuration.

Agreed, you need to ignore the stamp design that you see bleeding through the back, it can be misleading.

Here are the following tests I use, in order of preference:

1) wetting/drying test used by Tedski, obviously don't use on gummed stamps, in this case inconclusive, but...
-- for tough stamps, blot the stamp very dry with paper towel first until no moist spot can be seen on the paper towel, then let stamp sit loosely on flat counter top and watch (it shouldn't take long); if stamp is too wet, parts of the paper will stick to the table surface and yield flaky results
2) hold up to light and observe white margins from back (difficult if you have small margins)
3) use retro-reveal
4) (difficult to see on stamps because of size) use Q-tip and wet 2 adjacent white margin edges (not the central area with the stamp design) -- edge that starts showing a little "waviness" as it starts to dry (do not wait until completely dry) is the edge perpendicular to the grain direction
5) (not reliable as exclusive test because it is highly dependent on whether they folded the perforations before tearing) -- look at the perforations, edge parallel to the grain tends to have teeth tips that tear more evenly

I can only do 3 & 5, and to me (non-expert, bad-eyesight opinion), it appears the grain is horizontal. But better to try to confirm using #1 dabbed very dry if you haven't done that already.

[youpiao]

Nice point to remember, about the perf edges.

I was leaning towards horizontal grain, though the point is rather moot for this stamp, considering the condition.

Thanks, Dr. k

[I.M. DeBear]

When checking papers, my first step is always to hold the item up to a strong light. With the application of shade and various light angles, this technique can often reveal quite a lot of information about the mesh, fibers and other characteristics of the paper.