If you enjoy using vintage fountain pens, or any fountain pen that stores ink in a sac, you are probably very careful about what types of ink you use in those pens. They are typically more difficult to clean than a pen with a converter or piston fill mechanism. You might have also heard stories about ink sacs being destroyed by modern, high-saturation fountain pen inks. Is this true? Will a sac actually melt if you use the wrong ink in it? To get some answers, I decided to do a test and see what happens to fountain pen ink sacs when exposed to certain inks for extended periods of time.
The Idea Behind This Article
It doesn’t take much digging to find horror stories about people who used a particular ink in their fountain pen, only to find that it melted the ink sac. In pretty much every example, it was a vintage fountain pen and a modern, high-saturation ink. Even Richard Binder, a well-respected nib grinder and pen-repair expert, has significant experience and evidence that this happens.
I don’t doubt that it happens. While I have used many different inks in many different pens with sacs and have never experienced a meltdown in over 20 years of fountain pen use, it obviously happens to some people. I wanted to see if I could recreate a sac meltdown for myself. While my test and methods are in no way very thorough or conclusive, they are still worth mentioning for anyone who might be curious.
Also, I should make sure you know what an ink sac is. Basically, it’s a soft bladder that stores ink inside of a fountain pen (not to be confused with an ink cartridge). They’re typically found inside of almost every vintage fountain pen, but may be found in a few newer pens as well. If you’re still not sure what I’m talking about and want a photo, take a look at my visual glossary for fountain pens and scroll down to the word “sac”.
In order to see if I could get ink to melt a sac, I needed two things: ink and an ink sac. Since I restore my own pens I had plenty of new ink sacs sitting around. I also have a good selection of fountain pens inks, but not just any ink would do for this test. According to Richard Binder, inks that are more alkaline are more likely to damage the sacs. Looking at his list of different ink pHs, I realized I had a few inks that were highly alkaline. Specifically, I had a bottle of Iroshizuku Yama-budo with a pH of 9.47 and a sample of Noodler’s Apache Sunset with a pH of 8.4. I also wanted to try out a few high-saturation inks just to see what happened, so I also used Diamine Majestic Blue and J. Herbin Emerald Of Chivor.I wanted to do a long-term test, so I added some ink to 5ml sample vials to prevent evaporation. I cut a new sac into four equally-sized pieces and hooked each one onto a paper clip. The paper clip was purely to make it easier to fish the sacs out of the ink. I submerged the sac 3/4 into the ink and let it sit. Periodically I would check each sac to see if anything had happened to it. I started out checking the sacs every week and my results looked something like this:
- Day 0: Filled the vials with ink and partially submerged the sacs.
- Week 1: No change to any of the sacs.
- Week 2: No change to any of the sacs.
- Week 3-6: No change to any of the sacs.
- …Week 20: No change to any of the sacs.
They’re not pretty, but they’re not melted. Initially, I expected to see the sacs dripping off of the paper clips or just find a puddle of goo in the bottom of the vial, but that’s not what I found at all. Each sac was pliable and I was able to stretch each one without any ill-effects. Surprisingly, the paper clips are more damaged than the sacs themselves. Just to make sure everything was as it seemed, I washed off the sacs and took a good look at them. As I thought, they looked just fine.
So what’s going on here? Is it safe to use these inks in pens with sacs? Based on these results, I would say yes, but I think there’s more to it than a simple yes or no. My main caveat is that I used a brand new sac for this test. Would the results have been different if I had used a vintage sac that was 50 years old? Maybe. What about a sac that I had replaced a few years ago? What if I had a new sac but from a different batch? What about different inks? There are lots of variables here that I didn’t test, but I think the important thing is that these sacs were not at all damaged by these inks. What’s that tell me? It’s not a foregone conclusion that you’re going to melt your sacs simply by using particular inks. While it is possible, it is not necessarily going to happen automatically or quickly.
At the end of the day, you shouldn’t use any inks in your pens that you’re not comfortable with. This should go without saying. But you should also feel free to use any inks you want with your pens, as long as you know the potential risks that are involved. Personally, I wouldn’t use any “risky” inks in vintage fountain pens unless I knew that they had a new sac installed. Even then, I might choose not to use them, not out of fear for the sac, but simply because of the difficulty involved in cleaning highly-saturated inks out of particular pens. Ultimately it comes down to what your comfort level is and how much of a risk you want to take with your pens.
Hi, my name is John. I’m a Colorado-born professional photographer who recently moved back to Denver after spending 3 years in San Francisco. I’ve been using and collecting fountain pens for over 20 years. I got my first one in college when I got bored taking notes with ballpoints and pencils. Since then I’ve bought and sold hundreds of pens, but have consistency in my love of Esterbrooks.