Ink Sac Replacement Tutorial

My talented and kind friend Rob offered to show me how to re-sac a vintage Esterbrook using my recently acquired purse pen. He was also kind enough to let me document the process.

This process should basically work for any old pen that uses a rubber sac bladder. Just make sure to find the right sized ink sac (there are vendors who sell them on ebay).

Shall we begin?

1. scrape off old ink sac

Step 1: get that pen open and scrape off the old calcified sac. A standard X-acto or other utility knife works great.

2. measure  new sac

Step 2: insert the new ink sac into your pen to determine how long it can be and how much of the excess needs to be trimmed off. Rob is a pro so he just eyeballed it. If you’re doing this for the first time, I recommend using a piece of chalk or white pencil to make a mark on the sac so you don’t misjudge your cut.

3. leave a little room

Step 3: Rob is aligning the pen body with the nib unit and the sac to help make sure he is trimming the sac low enough to accommodate the extra space needed for the nib unit itself. Can you see the two ridges on the black nib unit? The ridge closest to the top of the photo is where the ink sac is to be placed. The addition ridge area is what is inserted into the body of the pen so Rob is accounting for that additional half an inch or so before trimming the ink sac. (This is the measure twice portion of the lesson.)

4. cut sac to the right length

Step 4: Using the same X-acto or utility knife,  trim off the excess sac (you are trimming the excess from the open end of the sac… just sayin!)

5. use shellac as glue

Step 5: Then using shellac (a small can purchased from the hardware store of Home Depot — a pint can should last you a lifetime) and a toothpick or wood dowel, apply a light coat of shellac around the area on the nib unit that you scraped the old sac from. Keep a towel handy as you don’t want to get any into the pen feed or onto the grip area where it might mar the finish of your pen.

The reason we don’t recommend a q-tip or brush is so that you don’t get any stray fibers into the sac or nib unit.

6. pull sac open

Step 6: Then, using reverse pliers or a homemade tool, pull open the ink sac so you have room to get the nib unti onto the sac (or vice-versa).

7. carefully put sac over nib unit

Step 7: Slide the ink sac over the nib unit.

8. make sure sac is flush to the top

Step 8: Once you remove the pliers, wiggle the sac on the nib unit until its as flush as you can get it and as even as you can make it.

Now comes the hard part. You need to wait to fill your new ink sac until the shellac is completely dry. Be patient, it’s worth it. I let mine sit for a day just because I was busy but Rob suggests waiting at least a couple hours.

Once its dry, reassemble your pen and fill it with ink. Do a little happy dance.

Tool for adding sac

Finally, I wanted to include an image of the homemade reverse pliers that Rob uses. He was given this amazing gift by Calvert Guthrie, lettering artist extraordinaire.

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7 comments / Add your comment below

  1. I just got a vintage Waterman Lady Patricia fountain pen and it’s working however I’m wondering if I should change the sac or get it professionally checked out. Thank you for the thorough tutorial!

  2. How wonderful, thank you both for this tutorial! I have been thinking I really need to learn how to re sac a pen but have been avoiding it because I really haven’t a clue how to approach it. This has been very helpful to boost my confidence. Seems straight forward enough! Thank you again!

  3. Thanks so much for this tutorial and the photos! I have just such a sac replacement project for an old fountain pen I’ve been wanting to try out but have been reluctant to tackle the task until now – your post is most encouraging that it’s a simpler project than I expected. By the way, that home-made tool, the reverse pliers, looks like a re-purposed tea leaf infuser…think I have one of those I can modify, too. Thanks!

  4. I managed to replace a sac without shellac on a Tip-Dip since it had a tight fitting metal sac protector that slides over the lip holding the sac.

    1. Jesi I think uses the latex sacs for Esterbrook pens, I like the silicone because they are translucent and easier to see how much ink I have left.

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