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Richard Binder's website

How to Replace a Fountain Pen Sac
Hands-on pen repair tutorial!
from the fountain pen of Richard Binder
Every lover of fountain pens (that’s you, or you wouldn’t be reading this) runs up against a pen that would be perfect if it only had a brain—er, a sac. A surprising number of pen collectors seem to shy away from pens that need any kind of repair, even something as simple as the installation of a new sac. My own collection, for example, includes a 1934ish Marine Green humped-clip Sheaffer’s Senior Balance that I snapped up at a bargain on eBay because the seller said it needed a sac. That innocuous disclaimer was apparently enough to scare off the competition.

For most pens, installing a new sac is about the easiest fix-up you can make beyond a little judicious polishing. If you’re game to try it, read on. You might buy a couple of cheap pens on eBay to teach yourself the ropes before attacking your minty red ripple Waterman’s Ideal No. 7 with the Blue nib. Wearever, Epenco, and Tuckersharpe are some cheap names to look for, and there are countless no-name junkers that go for less than $10.00. If you get pens that have sacs, you can easily rip ’em out. This, too, is part of learning to resac a pen.

Tools and Supplies

First, you need a supply of sacs. No problem. My vendor of choice is the Pen Sac Company, but you can also buy them from Fountain Pen Hospital, Pendemonium, Wood Bin Ltd, and other places as well. Addresses for all the suppliers I mention are at the end of this article.

The Pen Sac Company sells a bewildering variety of sacs and Vacumatic diaphragms. (“Diaphragm” is what Parker called the rubber doohickey in a Vacumatic so they could advertise the pen as being sacless.) They offer a couple of assortments as well as individual sacs. Their catalog includes several pages of information showing which sacs go into which pens. (There may be exceptions on a per-pen basis; the catalog says to use a No. 21 necked sac for a hard-rubber Duofold Junior, but I couldn’t even get a No. 20 to fit into the barrel of a Junior I resacked last week.)

Next, you need sac cement. Some pen suppliers can sell you small bottles of sac cement; Fountain Pen Hospital offers a 1-oz bottle with an applicator brush for $4.95 plus shipping. Being a professional cheapskate, I ran down to my local paint store and handed over about five bucks for a half-pint can of orange shellac, which is what the pen companies themselves used. I have enough shellac to last until my 273rd birthday. On the other hand, I don’t have that nice applicator brush, so I have to resort to subterfuge. I use toothpicks.

Steal your spouse’s talcum powder. Do not use baby powder or ladies’ dusting powder! These products are oiled to protect delicate skin, and oil eats rubber. Pen sacs are rubber... If there’s no plain talcum powder in the house, go buy a can.

The last pen-geek item you’ll need is section pliers. Many pens—most, really—don’t call for the big guns, so you may not need section pliers immediately. When the time comes, you can buy very good ones from Fountain Pen Hospital (shown here) or from Father Terry Koch.

If you have a bench grinder, you can make your own section pliers out of garden-variety slip-joint pliers from a hardware store and some rubber tubing from an auto parts store. If you go this route, you’ll need two pieces of tubing, each about an inch long, of a size to slip securely over one jaw of the pliers. Grind the teeth off the concave serrated part of the jaws, leaving a smooth curve, and slip one rubber onto each jaw. Position them so that they cover the part of the jaws that you ground smooth; that’s the area in which you’ll grip a section.

Okay, you have the tools (with one possible afterthought, of which more below). Sit yourself down at a well-lighted table or desk, and we’re off.

Disassembly, Cleaning, and Sac Removal

The first job is to get the old sac out. This means taking the pen apart. Most pens have a section that is a slip friction fit (just pushed into the barrel), but some (notably button fillers, Touchdowns, and Snorkels) have a threaded section that screws out. Virtually all lever fillers, except a few early Sheaffers, are a slip fit. For simplicity, I’m going to describe only the typical slip-fit lever filler in this article. (If you decide you like this kind of work, get a copy of “Da Book,” Frank Dubiel’s indispensable guide to fountain pen repair, and let Frank show you how to handle the more esoteric pens.)

Use your fingers to rock the section gently back and forth sideways, pulling as you rock, to break it loose. Don’t rock too far or you risk cracking the barrel!

If it refuses to budge after you’ve applied as much force as you dare, you can resort to section pliers. Grasp the barrel firmly in your closed fist. (You can enhance your grip by using a rubber kitchen jar-lid gripper.) With the other hand, apply the section pliers to the section, and repeat the rocking/pulling action, twisting a little as if to unscrew the section. If it’s a slip-fitter, it’ll come loose unless it’s been shellacked in place. In that case, you’re better off leaving it to a professional. Yeah, I know, you just blew the price of a pen on tools. Use them on the next pen.

With the section loosened, you should be able to work it gently out of the barrel. Use your fingernails to scrape all remaining fragments of the sac from the end of the section (the nipple). You need to get the nipple as clean as possible so the new sac will adhere properly. You can use a sharp kitchen knife to do further careful scraping, and you can use rubbing alcohol as a solvent. But don’t use alcohol on a visulated section; the plastic used for visulated sections is likely to be soluble in alcohol!

This is your opportunity to do your pen a favor by giving it a thorough cleaning. Drop the section assembly into a bath of Formula 409 for five or ten minutes, then scrupulously clean off any ink residue and the 409. This means flushing water through the system, which you can do by taking a mouthful of water and forcing it into the section from the sac end. When the assembly is clean, dry it thoroughly; blow some air through to dry the inside.


Formula 409’s principal ingredients are hazardous. They can cause skin or bone marrow damage, or cancer. The product is safe under normal household usage, but you might want to wear rubber gloves when soaking pens in it.

Clean the cap the same way, paying particular attention to getting the ink out from inside the cap. One way to do this is to use a paper napkin. Twist one corner of the napkin into a long thin spear, and insert it into the cap with a screwing motion. Turn in the direction that will keep the twist tight. Drive the paper as far down as you can get it. Repeat as necessary.

Now, if the sac didn’t come out in one piece, extract its remains from the barrel. A long thin alligator pliers, such as you can get from Fountain Pen Hospital or Widget Supply, can be helpful here but isn’t a necessity. If the sac is ossified, you can probably just dump out the chips. Occasionally you’ll run into a sac that has managed to glue itself, whole or in pieces, to the inside of the barrel. This can get ugly. I use various “afterthought” tools such as dental picks and scalers to chisel pieces of sac away from barrel walls. Take your time; as with the nipple, you want to get the barrel clean. Be careful not to damage the filler assembly.

If the old sac died and dumped ink all over the inside of the pen, clean the barrel in 409, too. You may also find that using 409 on a barrel will make it easier to extract glued-in bits of sac. Get the barrel absolutely dry afterward; any moisture left inside can corrode the parts of the filling assembly.

Sac Selection and Installation

With everything clean, you’re finally ready to install a new sac. If you don’t know the right size, try different sizes (you bought the assortment, right?) until you find a sac that just slips snugly into the barrel with the filler assembly in place. Then choose a sac two numbers smaller; if a No. 18 fits snugly, use a No. 16. You need to leave air space between the sac and the barrel to keep the pen from transferring your body heat into the sac when the pen is in your pocket. If the sac gets warm, the air in it expands, and it can force ink out through the feed. This makes the inside of the cap very messy, which is why you just cleaned it. No matter what sac size you end up with, it needs to be a stretch fit over the nipple. If you’ve chosen too small a sac, you may have to go up one size. You can try stretching the end of the sac over the nipple to verify that it’ll go.

The sac needs to be the right length. Most sacs are “straight” sacs; that is, the diameter of the sac is the same along its entire length. Sacs are made much too long; you will need to cut your new sac to the right length. To find how long it should be, slide it into the barrel, closed end first, until it hits bottom. Slide it back out about 1/8” (3 mm) so that it won’t butt against the end of the space into which it fits. Clamp it with your thumbnail right where it enters the barrel, and pull it out.

Still clamping it, hold it up to the section, lining your thumbnail up with the step on the section that seats against the end of the barrel. Now mark the point on the sac that corresponds to the step between the nipple and the part of the section that fits into the barrel. This distance will be between 1/4” (6 mm) and 1/2” (13 mm).

Cut the sac at this point, being careful to cut straight across.

If your pen requires a necked sac (with the open end smaller than the diameter of the rest of the sac, like the neck of a bottle), you must rely on the information in the Pen Sac catalog or else measure the space into which the sac fits and then choose a sac of the proper length. You don’t cut necked sacs; they have to fit right. This may mean that you can’t order the exact sac you need until you’ve taken the pen apart.

With the sac ready to install, apply a small amount of sac cement (shellac) around the outside of the nipple. Be careful not to let the cement get into the inside; it’ll clog the feed—possibly permanently! Spread the open end of the sac, stretch it over the nipple, and adjust it so that it’s pushed all the way down and is seated against the step. If you find that you’re a little clumsy and have trouble fitting the sac in place, you can buy a sac spreader. Pendemonium offers these little gems for $5.00. I recommend that you buy yours yesterday, as today—with wet cement drying on your pen—isn’t the best time to go shopping. The sac should stand straight up, in line with the section, and the stretched part should be symmetrical on all sides. (The sac shouldn’t be pulled over toward one side of the nipple.) If you like, you can run a very small bead of cement around for an improved seal right where the sac butts against the step.

Once the sac is installed properly, put the assembly down. Go away for half an hour to let the cement dry. It doesn’t necessarily take half an hour, but if you adhere to a firm half-hour waiting period, you’ll never proceed too soon. Getting itchy and proceeding too soon means having a still-wet sac come off in your hands or leak in the pen or—worst of all—glue itself inside the barrel.

Now cover the new sac with a thin coat of talcum powder. This will make it slide into the barrel more easily, and the filler will also work a little more smoothly. Reinstall the section into the barrel, aligning the lever with the nib as you go. There’s no need to cement a hard rubber or ordinary plastic section in place unless it’s close to falling out, but Sheaffer has always recommended that visulated sections be shellacked in. If your section is so loose that it really does fall out, try shimming it with a bit of paper.

Et le voilà! You’ve just accomplished a task that used to require the services of a highly paid professional. You’re on the road to restoring your way to a better pen collection. Fill your revitalized pen and enjoy the ride!


Fountain Pen Hospital
10 Warren Street
New York, NY 10007-2218
Phone: 212-964-0580
Toll-free: 1-800-253-PENS
Fax: 212-227-5916
Email: fountainpenhospital@att.net

Phone: 319-372-0881
Fax: 319-372-0882
Email: info@pendemonium.com

Father Terry Koch
P.O. Box 128
Los Gatos, CA 95031-0128
To receive his catalog of tools and parts, send him a large envelope with two stamps on it (USA).

The Pen Sac Company
P. O. Box 4470
Carlsbad, CA 92018-4470
Phone: 619-729-6894
Toll-free: 1-888-PENSACS
Fax: 619-931-5845
Email: PenSacs@aol.com

Widget Supply
P. O. Box 3282
Albany, OR 97321-0710
Fax/Voicemail: -541-924-8882
Email: widget@proaxis.com

Wood Bin Ltd.
R.R. # 6, Simcoe
Canada N3Y 4K5
Phone: 519-428-2555
Fax: 519-428-6311
Email: woodbin@simcom.on.ca

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