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"baby's Bottom" Explanation, Please...


7 replies to this topic

#1 Christopher Godfrey

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Posted 16 January 2020 - 15:31

I wonder if someone would define this expression for me?  That I know of, I have never experienced this on any pen I have ever owned; but (but...!) I am wondering if I have it on my Pelikan M1000.  The pen often has trouble starting and runs dry all the time while I write (just suddenly goes quite dry).  Now, my fine nib is rather flexible, even for a M1000, and I assume, for starters, that the feed is not keeping up and I am certainly awaiting an announcement from Joey Grasty that his replacement feed is available (it seems to have been on the cards for a long time and his website still says "November 2019").

 

I write at an angle of perhaps 35-45 degrees from the horizontal and I do not rotate my pen.  However, I notice that if I hold the pen more upright the ink flow seems to improve slightly...perhaps this has some bearing on matters?  I bought the pen used some months ago, so have no idea about previous owner's habits.

 

I know: photos would help...I shall work on that later...meanwhile: any ideas, please?



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#2 DonM

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Posted 16 January 2020 - 18:09

Take a look at your M1000 to see if the feed mates properly with the nib.  I had to return an M1005 because there was a gap between the nib and the feed.  The nib touched the feed at the tip, but behind that there was a gap that could be seen if you held it up to the light and looked at it from the side.  Wrote great right after I filled it, but as soon as the ink that was present under the nib was used up the ink no longer flowed.  Sounds like the same thing you are describing.



#3 BaronWulfraed

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Posted 16 January 2020 - 18:43

Running dry /while/ writing is unlikely to be "baby bottom".

 

If you look tangent to the contact patch of the nib (looking at the end, across the angle you write), "baby bottom" would appear as extreme

 

|(

|(

 

(where | is the paper, and ( is each tine). I say "extreme" as the ink surface tension/viscosity might affect occurrence. Basically, if the surface tension draws the ink up away from the paper contact one gets hard starts. Once the paper touches the ink (which may require some pressure) surface tension holds the ink into the gap and down to the contact patch.

 

Some curvature is possibly desirable -- as a sharp corner could snag on paper fibers; but it should not be so much that the ink surface does not make it to the contact patch.


Edited by BaronWulfraed, 16 January 2020 - 18:44.


#4 Ron Z

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Posted 16 January 2020 - 19:14

Baby bottom is how we describe it when the inside radius of the nib is too big.  The inside edges should be slightly rounded so that the nib does not scrape or grab the paper as you write.  But if the inside edges are too rounded the ink pulls back a bit from the tip, withdrawing enough that the ink is suspended in the slit and doesn't make contact with the paper when the nib touches it.  A little pressure on the first stroke lowers the ink down to the paper and often gets it writing again, until you pause for  a moment.   This is sometimes caused by over polishing the inside of the nib, or aggressive polishing the nib on a softer material like Micro-mesh.

 

The solution is to have a skilled pen mechanic or nib tech shave a little off of the "cheeks" and then polish the nib a bit, so that it writes consistently. 

 

If on the other hand, the nib starts most of the time, but stops in the middle of a line and has to be primed again, or doesn't start when you press harder, then I would look first to the set of the feed against the nib or a feed that is off center, and then at a contaminated or clogged feed. 

 

You should not be able to slide a piece of paper between nib and feed.  If you can, then the set of nib and feed needs to be corrected.  If you can't I would clean the nib unit in something like RapidoEze pen cleaner.

 

DO NOT use dry heat to set the nib and feed.  The fins on the collector can be easily damaged by dry heat.  Boiling water is a bit tricky - evidently people forget that hot steam rises off of boiling water, and I've heard of folks dropping the whole pen in the water when they burn their fingers....


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#5 Ray-Vigo

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Posted 16 January 2020 - 21:22

Ron has a good description of the "baby's bottom" problem. The only thing I will add is that, in my experience, it tends to happen more on modern pens than on vintage ones, and even "premium" nibs (e.g., higher-end gold nibs) can have the issue as they come from the factory. My guess is the manufacturers are going too far toward making a ball-ended nib feel ultra-smooth. I'm sure there are vintage pens out there with the issue, but all of the baby's bottom nibs I've had were modern, rigid nibs with ball tips that had been over-worked at the bottom of the ball where the tip meets the paper.



#6 sansenri

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Posted 16 January 2020 - 22:03

plus add the very likely fact that, besides the design of the tip that was usually more squarish, in vintage nibs, that have actually been used, the miles of writing will have worn off any baby bottom that may have been there...



#7 Ron Z

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Posted 17 January 2020 - 02:05

Ron has a good description of the "baby's bottom" problem. The only thing I will add is that, in my experience, it tends to happen more on modern pens than on vintage ones, and even "premium" nibs (e.g., higher-end gold nibs) can have the issue as they come from the factory. My guess is the manufacturers are going too far toward making a ball-ended nib feel ultra-smooth. I'm sure there are vintage pens out there with the issue, but all of the baby's bottom nibs I've had were modern, rigid nibs with ball tips that had been over-worked at the bottom of the ball where the tip meets the paper.

Yup.


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#8 Christopher Godfrey

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Posted 17 January 2020 - 05:48

Thank you, all, for the thoughtful and helpful responses!  At present I have no further report to make and no photos; but it seems more likely that the offending pen will soon wend its way to someone with more experience than myself!

 

BaronWulfraed's and Ron's description's were particularly clear and I am inclined to dismiss baby's arse (I mean bottom) as my problem...meanwhile: thanks again, all!





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