Baseballs and black light

I’m going to start by showing you something really cool, and then I’m going to explain it…

Check out this photo that I took of some baseballs under a black light:

Do you see the “1297” on the left side of the photo? Do you see the other faint numbers that appear to be illuminated? That’s invisible ink. It only appears under ultraviolet light.

Let me show you a couple more pics…

Remember when I caught Barry Bonds’ 724th career home run on 8/16/06 at PETCO Park?

Here’s a side-by-side photo of that ball. The image on the left shows it in normal light; the image on the right shows it under a black light:

I learned about the invisible ink while doing research for my new book — and then I got to see the ink being stamped on the balls when I visited the Rawlings baseball factory in Costa Rica.

There are 350 employees at the factory who do nothing but stitch baseballs all day — by hand. Every employee has a stamp with a unique serial number. When the balls are done being stitched, they get stamped with invisible ink. That way, if an inspector finds a “correctable flaw” on a ball (for example, a stitch that’s not quite tight enough), he can examine it under a black light, mark down the serial number, and send it back to the person who stitched it. It’s basically an extra method of quality control.

Even though every ball gets stamped with the ink, you won’t always see it on the balls you get a hold of — that is, if you bother to go out and get yourself a black light. That’s because every ball gets wiped with a cleaning solvent at the factory. The purpose of the solvent isn’t to remove the invisible ink. Rawlings doesn’t care about that. The solvent is used to remove excess wax or oil that might’ve found its way onto the cowhide cover, and in the process, the invisible ink is often rubbed off.

Now, how about some more photos? Here are some balls in regular light…

…and here they are under a black light:

For an extra cool effect, download the previous two photos so you can open them both at once and flip back and forth.

I was absolutely stunned when I shined a black light on my baseballs for the first time and saw all these little serial numbers appear out of nowhere. I had snagged thousands of balls over the course of two decades, and I thought I knew everything about them, and then I discovered this whole secret element to my collection. It was like…I don’t know…not to get overly dramatic or anything, but it’s like I’d stumbled into an alternate reality. Of all the things I learned while doing research, this was definitely my favorite.

More pics?

Let’s take a look at the two commemorative balls that Heath Bell gave me on 7/23/09 at Citizens Bank Park. Here they are in regular light…

…and here they are under a black light:

As you can see, there’s a very faint invisible ink stamp on the World Baseball Classic ball — just to the left of where it says “official ball.”

Here’s a closer look at the brighter stamp on the right:

I’m not sure what it says or how to decipher it.


Is that a period after the 8?

You know what? It doesn’t even matter. It’s just awesome. Let’s leave it at that.

Here’s one more photo for you:

I like the stamp on the lower left that simply says “6-11.”

See the one just to the upper right of it that says “036I”? That’s a 2008 All-Star Game ball, in case you were wondering.

That’s pretty much it, but let me just say quickly (for those who don’t know) that my new book is called The Baseball, and if you’re interested in checking it out, here it is on Amazon. Chapter 7 is called “The Rawlings Method,” and there’s a TON of info about the entire manufacturing process — stuff that some people might find hard to believe.


  1. bigglovebob

    Z-Man- you outdid yourself on the book man! I am loving it. I can tell that it was a labor of love. I know your dad is looking down and beaming with pride. Take care!

    Big Glove Bob

  2. cookandsonbats

    That’s really cool, Zack. I guess your stats aren’t complete. You better track all of the serial numbers on your balls to see how many you have from the same worker(s). That would be really cool to find (for example) that the same guy stitched a ball you got in the world series in 2008 and a baseball you got at…oh, let’s say…the Kingdome in whatever year you went to the Kingdome. You get the idea, right? John is right…I think Tim and I are going to have to go get a black light.

  3. zackhample

    Coming from someone like you who (if I’m remembering correctly) hardly ever reads books, I take this as the highest possible compliment. My dad lived long enough to see me get my first royalty check for “Watching Baseball Smarter” last summer. I think he took great pride in seeing that and knowing that I had really established myself as a writer.

    Months ago, I actually did joke with some friends about buying black light stock. Think it’s too late?

    Oh jeez. I’m nerdy and obsessive, but not THAT nerdy and obsessive. Fun idea, though. You guys should definitely get a black light.

    Whoa! How do you find all this amazing stuff online? You truly have a gift.


    You know how you’re gifted at snagging baseballs, and Kobe Bryant is gifted at basketball. I guess I’m just gifted at finding random things online. (Does this mean you’re actually going to get one? Or you just think it’s cool?)


    Zack, i am honored to have a copy of “The Baseball” (i won’t use the subtitle, because they are stupid). i am delighted with your work, and always proud to know you.
    However. . .
    i’m wondering if you can answer the following questions:
    “Why should a man carry away an object worth $2.50 just because he gets his hands on it? (“Cap” Huston)
    “When people go to a restaurant, do they take the dishes or silverware home for souvenirs?” (Huston, again)
    Why don’t y’all just call yourselves “Ballhogs”, instead of “ballhawks”? (jgk)


  6. bigglovebob

    Zack- you’ll have to keep me in the loop about any road trip plans this summer. I currently have 4 trips planned to see the Twins. 3 trips to KC and 1 to Milwaukee where I hope to hook up with Happy for the third year running. If you make it anywhere in the midwest I will be really tempted to hop in my buggy and meet up with you for a series.

    Big Glove Bob

  7. kslo69

    Howdy over there, Zack! I hope all is well with you and yours. I just picked up a copy (really 2), and I am looking forward to reading it with my son at bedtime tonight. Congratulations!
    After reading your latest entry, is there any coding that would tell you which balls are used by the MLB? You can guess where I’m going with this…
    Cheers sir. You are becoming a true Baseball Historian.

  8. mrespot

    Interesting entry…got your book Wed. and just finished it Saturday. Loved the book! It was like going to the movies, I was lost in another world. One of the best books I have ever read. What game are you going to first in the 2011 MLB season?

  9. gu3_

    If it means anything, I think the WBC ball is upside down. Turn it over and the number would read 1808. The end of the stamp just merged with the 1.

    And I think I’m definitely going to do what Matt mentioned! I always wanted to mark my balls but never wanted visible ink.


    this whole black light thing is really awesome!
    it just so happened that my friends were throwing a highlighter party the day u blogged about this so i got to check it out right away. random thought though – does anyone know if the marlins will be using a commemorative ball this season, since its their last season in this ballpark?


    HI from AZ ZACK, IVE been to 15 games so far and caught 2HR S.AND 1 DOUBLE .cws vs the milledge HR.3/14/11. WE BOTH TOOK OUR LIDS OFF..i got the ground rule double after the hr so i tried for the trifecta.a foul ball too.didnt happen.good job on the book andthanx for the shout out…..TC 206 OUT

  12. zackhample

    Good analogy. Not sure if I’ll actually get one of those pens. I’m feeling too lazy at the moment to go for it. Maybe I’ll start marking the balls that way after I snag No. 5,000.

    I am honored to know that you have a copy of “The Baseball.” I must admit, though, that I can’t answer those questions. I suppose we ARE a greedy bunch. :-)

    Cool. Will do. I haven’t booked a single game yet for this coming season, but I might end up going on a mega-road trip in August and September. Stay tuned. And whoa, just watched that YouTube vid. That’s insane! Thanks for sharing. I can’t believe I never saw it ’til now.

    Thanks for getting (not one but) two copies of the book. I’m not quite sure what’re getting at with your question. Either I’m really dumb or you just need to be more specific. Either way, can you help me out and explain what you mean?

    Glad you enjoyed this entry and (more importantly) the book. Lost in another world? Damn, man, I’m flattered. Not sure about my first game yet for 2011. Possibly the Twins at Yankee Stadium on Monday, April 4th.

    Hmm, you might be right about the WBC ball. Still hard to tell. If you do get one of those pens, please show it to me when I see you.

    Nice timing with the highlighter party. Did you, in fact, find some baseballs with good invisible ink stamps? As for the Marlins, yeah, I’ve heard that they WILL be using commemorative balls.

    When you’re the man, you’re the man. Thanks for checking in and congrats on the snags. Hope to run into you this year. If my friend Brandon has his way with me (and I mean that in a nonsexual way), I’ll end up in San Diego for about a week.

  13. kslo69

    More specifically, would the coding help you towards getting recognition from the Guinness Book?


    Yeah I was able to find a few near perfect invisible ink stamps. Also, on the opposite side of the ball from the stamped ink number, (on one ball in particular) it seemed as if there were a couple other strange invisible ink markings including possibly a url. I’m not exactly what it says, I’ll have to do some more investigation/comparisons next week when I go home for break.

  15. zackhample

    Interesting thought. I hadn’t considered it. But the people at Guinness simply aren’t interested. If they were, they would reach out to me again as they did in 1999 instead of ignoring me and making my claim virtually impossible to prove.

    Whoa, a URL?! That’s bizarre. Please please please take a pic of it and send it to me. I’m dying to see that.

    I feel sorry for Mister Wade.


    YOU THE MAN. DO you like it when yor dog scraps lies on his back? i just saw AIRPLANE.I WANT TO SEE THEM MAKE airplane 3…i speak jive

  17. Adam

    Last week I read your post from 9/2005 about how you wanted to visit the Rawlings factory in Turrialba and then the post where you went, but today I looked for them again and they are gone. The link from this page doesn’t work, either. What gives? I wanted to use them in my class: I teach English at the Turrialba plant where the balls are made and your blog has good material for my upper-level students. They are surprised to learn that others are so interested in their craft.

  18. Charlie Light

    Hey Zack,
    That sounds awesome. Very nice photo, and a great album cover. I haven’t commented in almost a year, though I’ve read off and on. I just started a new blog, and I used your name in it (included a link to your blog as well). I also put down the picture from the NY Times article on you from 2006. Is that alright with you?

    See ya Zack

  19. Zack Hample

    I don’t know what to tell you. The links seems to be working fine for me. Sounds like you have a REALLY cool job.

    Totally alright. Thanks for asking. And wow, sorry for taking 8 million years to reply. Somehow I didn’t see your (or Adam’s) comment ’til now.

    Glad you like it.

  20. James

    I have some baseballs from the 50s and the 60s signed and I would love nothing more than to get them appraised. If you can help it would be greatly appreciated. #609-510-8380 I would truly appreciate a response Thank You!!

  21. Zack Hample

    Hey, James-
    If you’re in (or near) New York City, you could bring them to my family’s book store, the Argosy, where we deal with autographs, and we could take a look at them. Otherwise I would just suggest looking up sports memorabilia dealers near you and seeing if they can help.

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