(This page revised August 28, 2021)
I have a very nice Wahl Personal-Point Gold Seal pen in chased black hard rubber. This pen is a fine point and is an excellent writer. The problem with it is that after a few minutes of writing a blob of ink forms at the end of the feed. I have determined, with crude experiments, that the heating of the pen by my hand causes this. If I pre-warm the pen for a few minutes by holding it vertically in my palm with the nib up so that the heated air can safely expand out through the feed I can safely write without blobbing. This is quaint but not convenient. So I think that there are two other options for correction. Shorten the sac so there is less air to warm or use a narrower sac to provide an air space between the barrel and the sac. Which is the better solution or should I do both? Is there another fix or possibly another cause for this problem?
You have analyzed the problem correctly, and you have also proposed the correct solution. Note that I use the singular form here; there is indeed only one solution, which is to combine your “shorter” and ”narrower” options. The sac should not touch the back end of the barrel, nor should it be in intimate contact with the barrel wall. If the sac is in intimate contact with the barrel, it absorbs body heat and transfers it to the air within, which responds obediently to Boyle’s Law and expands as it is warmed. Air space insulates things to prevent the problem.
Most pen manufacturers and repairers in the old days, back before Noah came over on the Mayflower, had three criteria for determining the size of the sac for a given pen: ink capacity, ink capacity, and ink capacity. Over and over again I see pens whose sacs are almost molded to the inner contour of the barrel and pressure bar; they fill all of the space available. Bad idea, for the reason you have discovered.
These days, some pen repairers measure the diameter of the section nipple to determine the size of the sac that they should use. But this is, unfortunately, a bogus way to do things. For a twist filler, you want one size of sac, for a button filler a different size, and for a lever filler, a different size yet — in fact, any of several different sizes, depending on how bulky the pressure bar is. There has to be a better way.
There is. Instead of measuring the nipple, measure the available space in the barrel. With the pressure bar in place, find the largest sac that will drop freely into the barrel. Measure how far in it goes without stopping. Remove it and cut it so that there will be about " (3 mm) of absolutely clear space before it stops. This ensures that the back end will be clear of the barrel and the pressure bar. This sac will take some stretching to make it fit over the section nipple; that’s okay, and if necessary, you can hold it in place with cellophane tape while the shellac dries. This will give you time to clean your fingers of the shellac that got on them while you were struggling to make the sac stay on before you thought of using the tape.
One other thing. Some pens supposedly require specialty sacs. You often hear, for example, that you should use a necked sac in a Duofold. The purpose of using a necked sac in a Duofold is to fill up the entire barrel volume, and you now know why you shouldn’t do that. I keep no necked sacs except for Snorkels and PFMs/fat Touchdowns. But I do keep tapered (or tapered/necked) sacs for the few pens, such as the Eversharp Skyline, that can really benefit from the little squidge of extra ink capacity that you can gain without using a too-large straight sac that will get intimate with the back end of that tapered barrel.
I have several pens that are not as smooth as I’d like them to be. After I receive a new pen like that should I immediately send it off to an expert such as yourself for smoothing or should I allow some “break in” time first? If I should wait, about how many pages should I write with one before I send it off?
Whether you should send your pen off to an expert or smooth it yourself is up to you.
The implication of that bald statement is that smoothing is needed. Tipping material is very hard. Contrary to what some pen companies (the original Esterbrook among them) told their customers, a pen will not wear in during a few days or weeks of use. Even when used all day every day, a modern high-ruthenium alloy takes several months, or even years, to show perceptible wear. So “breaking it in” is not going to work.
Compounding the problem is the fact that a surprising number of nibs, especially on higher-end pens that are finished by hand instead of by machine, are scratchy because they’re misaligned. I know of one manufacturer whose italic nibs may all be misaligned in the same exact way. At least I’ve never seen an italic from this maker that wasn’t misaligned, and I’ve worked on a nontrivial number of them.
The inescapable conclusion is that if you’re not comfortable aligning and smoothing your own nibs, then you should send them off to a nib technician. I have several clients who figure the cost of nib adjustment into the purchase price of a pen, and many of these people actually have their dealers ship the pens directly to me. I’m quite sure other nib people have similar situations with some of their clients.
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