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How to Replace a Pen Sac

(This page revised June 30, 2021)

Reference Info Index | Glossopedia  ]

Fountain pen

It's tremendously satisfying to start with a pen that won't take ink and end with one that does. It’s always a good idea to learn by practice rather than waiting until a precious pen is on the line. To this end, I suggest you buy a couple of cheap pens on eBay or at your local flea market or antique mall to teach yourself the ropes before you turn your attention to your minty red ripple Waterman’s Ideal No 7 with the Blue nib. Arnold, 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. (I use the term “junkers” loosely, as you already know if you've read Don Fluckinger’s Extra Fine Points series on these pens.) If you get pens that have sacs, you can easily rip ’em out. This, too, is part of learning to resac a pen.

Tools Required

Parts Required (see footnotes for more information)

Supplies Required (see footnotes for more information)

Shown here, from top to bottom, are No 13, No 16 (latex and silicone), and No 22 straight sacs. At the bottom, for reference, are a Debutante Vacumatic diaphragm and a standard Waterman Ink-Vue sac.

An assortment of sacs

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 the ones shown here very economically.

Section pliers

For sac removal tools, I use various implements such as hooks and dental picks and scalers. Shown below are a hook and two dental scalers. Hooks are ideal for grabbing sacs and dragging them out of barrels. To make a hook, form a loop on one end of a length of heavy-gauge coat hanger wire for hanging and to provide a “hold onto”; form the other end into a hook and fire harden it by heating it red with a butane torch and quenching it in cold water; and then grind the hook point into a flattened scraper shape that can slip between a sac fragment and a barrel wall. Scalers are particularly useful when it comes time to chisel pieces of petrified-in-place sac away from barrel walls and section nipples. You can get dental picks from a variety of online suppliers, and you can reshape the tips to suit your needs.

Sac removal tools

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 detail the process only the typical slip-fit lever filler in this article. At the end of the article you will find a section describing how button fillers differ from lever fillers. For reference, here is a cross-sectional drawing of a typical lever filler.

Pen with cap removed
Before attempting to remove the section, examine the barrel/section joint, looking for cracks, crazing, signs of bulging or shrinkage, or the presence of adhesive. Cracks or crazing will make it difficult, if not impossible, to remove the section without damage. Bulging or shrinkage can make it more difficult to reassemble the pen after you replace the sac. The presence of adhesive will complicate things but usually will not prevent a successful repair.

First, assuming that you have decided to proceed, apply gentle heat to the joint. Using your heat gun, warm the barrel/section joint carefully, spinning the pen around so that all sides of it are heated evenly and testing frequently by placing it against your lower lip. (If it’s too hot to hold there briefly, it’s too hot, and you should allow it to cool a little before proceeding.) For a heat source, I recommend the “embossing” gun that you can get at craft stores (illustrated below). It‘s inexpensive and reliable, and you can control how much heat it delivers by holding the pen nearer to or farther away from it, as necessary.

Because heat does not conduct through celluloid instantly, it is generally better to warm the joint several times over a period of three or four minutes, allowing it to cool a little between applications of the heat.

Heat gun
Despite what you might have read in various repair books (including Da Book), do not use an alcohol lamp or other open flame. Celluloid is highly flammable! Even when you use a heat gun, it is wise to keep a bowl of water handy just in case you should happen to heat a celluloid pen to the degree that the celluloid begins smoking and hissing like a firework snake. You can’t blow this kind of fire out, but water will quench it.

Now try using 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!

Rocking the section out

If it refuses to budge, it’s probably shellacked in place. (Sheaffer shellacked Visulated sections but not hard rubber ones, for example.) You can resort to section pliers and a little more heat. Be very careful with the heat, as shellac softens at about 140° F (60° C) while celluloid begins to soften at about 165° F (74° C).

Grasp the barrel firmly in your closed fist. (You can enhance your grip by using a rubber gripper square, available from several online pen dealers, or a second pair of section pliers. The rubber gripper square is the better choice because it distributes the force, reducing the chance of crushing the barrel.) 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 heat doesn’t do the trick, do not persist.

Using section pliers

If it’s a slip-fitter, enough persistence will make it come loose unless it’s been glued, as many cheap pens were done during World War II. In that case, you’re better off leaving it to a professional. Yes, 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 or a sharp kitchen knife 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 your knife to scrape off the shellac that is probably there, and you can use rubbing alcohol as a solvent for this operation. But don’t use alcohol on a transparent section (or any other plastic section); the plastic used for these sections is likely to be soluble in alcohol!

Flushing a pen with an ear syringeThis is your opportunity to do your pen a favor by giving it a thorough cleaning. Drop the section assembly into a bath of INDY’S IDEAL PEN FLUSH or a dilute solution of clear household ammonia (not sudsy ammonia, and most definitely not the lemon-scented variety!) for five or ten minutes. Make the ammonia solution by mixing 1 tablespoon (15 cc) of ammonia with cup (158 cc) of water. After soaking the parts, scrupulously clean off any ink residue and the cleaning solution. This means flushing water through the system, which you can do by using an ear syringe to force water through the section from the sac end. (If you don’t have an ear syringe, you can use your mouth for this job.) When the assembly is clean, dry it thoroughly; blow some air through to dry the inside.

Clean the cap the same way, paying particular attention to getting the ink out from inside the cap. You can do this most easily with cotton swabs or a paper towel. Twist one corner of the towel into a long thin spear (sometimes called a twizzle), and insert it into the cap with a screwing motion. Turn in the direction that will keep the twist tight. Drive the twizzle 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. Long thin alligator forceps can be helpful here but aren’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. Take your time; as with the nipple, you want to get the barrel clean. Be careful not to damage the filler assembly.

Picking out bits of sac

If the old sac died and dumped ink all over the inside of the pen, clean the barrel, too. You may also find that using your soaking solution 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. For many pens, my Fountain Pen Sac Size Guide for Repairers will help you to choose the correct size sac. For pens that aren’t listed there, try different sizes (you bought the assortment, right?) until you find a sac that just barely slips into the barrel without being forced, with the filler assembly in place. Then choose a sac that's a little smaller. For larger pens, go down two sizes; if a No 18 fits snugly, use a No 16. For smaller pens, you can usually go down one size (e.g., from No 14 to No 13). 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 extra long; in most cases you will need to cut your new sac to the right length. (Very large pens such as a Waterman 58 are long enough that you can sometimes use the sac uncut.) 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.

Measuring a sac, step 1

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). In the illustration here, you can see a bright line where light is reflecting off the step between the nipple and the rest of the section.

Measuring a sac, step 2

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 can cut a very little of a necked sac’s neck, but cut too much and you’ll end up with a straight sac.) This may mean that you can’t order the exact sac you need until you’ve taken the pen apart.

Do not substitute any other adhesive for for sac cement. Some adhesives can damage pens, especially celluloid ones, and some will also gradually let go when exposed to ink.

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.

Installing the sac

Installing a sac on a Parker section with a Lucky Curve feed is a little different from the standard installation. Here is how to do this easily. Step numbers refer to the numbers in the image below the list:

  1. Evert the end of the sac and fold it over to form a “cuff.”

  2. Slip the open end of the sac onto the feed’s Lucky Curve.

  3. Apply shellac to the section’s sac nipple. Holding the section with one hand, use that hand’s index fingernail to flip the cuff over the nipple. Then, holding the flipped part in place, use the other hand to roll the rest of the cuff around the nipple.

  4. Straighten out the cuff if necessary, then adjust it on the nipple so that the sac is aligned with the section as nearly straight as possible.

Installing a sac on a Lucky Curve section

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.

The sac installed

Now cover the new sac with a thin coat of talcum powder (or graphite). This will make it slide into the barrel more easily. The sac will also repel moisture, and the filler will work a little more smoothly. Reinstall the section into the barrel, aligning the lever with the nib as you go. (Some pens, mostly English brands such as Conway Stewart, usually have their levers aligned on the underside, 180° away from the nib surface.) 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, you’ll have to shellac it in regardless of what it’s made of. Shimming with bits of paper can crack the barrel.


Button Fillers

As you might expect, you need to take a slightly different approach with a button-filling pen. For reference, here is cross-sectional drawing of a typical button filler:

Fountain pen schematic

In most button fillers, the pressure bar rests against a flat surface on the back of the section where it fits into the barrel. (See the diagram above and the photo below, the upper pressure bar.) If the section is threaded, as most are, unscrewing the section before you remove the pressure bar can twist the pressure bar inside the barrel, damaging the pressure bar, the section, the barrel, or all of these parts. Beginning c. 1930, Parker Duofolds have pressed-in sections. Initially, these pens had a metal “trough” screwed into the barrel to provide a rest for the pressure bar, which was cut slightly shorter; later versions have a shorter pressure bar that has its own support in the form of a strip coming back along the length of the barrel through the button hole, with a flange to catch on the edge of the hole. This later pressure bar is sometimes known as a “Mark II” type (below, lower).

Pressure bars

Some third-tier button fillers have pressure bars as described above, with press-fitted sections that are glued into the barrel. Among these models are the Wearever Deluxe 100 and most Arnold models.

In order to remove the pressure bar from a pen with a threaded section, you must first remove the button. In most button fillers, the button is simply pushed into the barrel. The button has cuts dividing it into four “fingers” that are slightly springy, with a little flange on the end of each finger. Pushing the button into the barrel squeezes the fingers until they clear the hole at the barrel’s end; once clear, they resume their normal shape and hold the button in place. Removing it without damage is best done with a Parker button remover; but if you do not have this tool, you can use Nylon or Nylon-jawed pliers. If you do not know in advance whether the section is threaded, take the button and the pressure bar out first.

Removing a button

Parker’s final button filler, the VS, came in two versions. The earlier version has metal threads under the blind cap, and these threads are part of a ferrule that holds the button in (below, left). The button does have the springy fingers and can be pulled out, but it is usually easier to unscrew the entire assembly. To unscrew the threaded ferrule, use a standard Vacumatic tool; the threads are exactly the same. Later VS pens have plastic threads (below, right), and for these pens you must pull the button out as on earlier Parker models.

Early VS buttonLate VS button

Third-tier button fillers with glued-in press-fitted sections often have buttons that fit tightly over the end of the pressure bar and cannot be removed through the back of the barrel. For these models, because you will not be twisting the pressure bar when you remove the section, the button and pressure bar are not a potential source of damage.

Some modern button fillers, such as those made by Filcao of Italy, have a threaded collar that holds the button into the barrel. The button in these pens is not split into fingers, and you cannot pull it out. Unscrewing the collar will free the button.

When reassembling any button filler, be sure that the pressure bar goes on the right side of the sac! For a pen with a threaded section, you should insert the pressure bar at an angle so that it contacts the barrel wall, then slide it down and into position. Complete the operation by reinstalling the button to keep everything in place.

  1. There are tables of sac sizes for various pens here. Sacs are available from several online sources. Silicone sacs are sometimes a better choice than latex because silicone doesn’t outgas sulfur vapor that can cause some celluloids to turn brown. It’s also transparent, a nice feature for demonstrator pens. But silicone is gas permeable, and if you store inked pens lying horizonally or nib downward, they will leak.  Return

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.

This article is also available as a chapter in The RichardsPens Guide to Fountain Pens, Volume 2, in either of two printed versions or as an ebook for your computer or mobile device.

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