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FAQ 7c3. One Word: PLASTICS

Some very helpful information about plastics used in mah-jongg tiles, from helpful posters on our Q&A Bulletin Board ...

Name: Mike
Email: drmike at
Date: 06 Aug 2002


Hi again Tom,

1. How to tell the difference between Catalin and Bakelite?

Tough one that, I will try to explain why. Bakelite and Catalin are both tradenames for early thermosetting plastics based on formaldehydes. Bakelite was manufactured by a US company, Catalin was manufactured in direct competition by a UK company. Actually the tradenames covered a range of different plastics: phenol formaldehyde, urea formaldehyde and melamine formaldehyde and don't refer to a specific compund. To complicate things further each of these plastics could be compounded differently by adding (or not adding) certain additional ingredients (called 'fillers' in the business, carbon black being the stereotypical example, added to increase strength and lower cost, but resulting in a darker coloured material). Right from the start plastics were tailored to a certain degree to get the kind of properties and cost wanted.

However, all is not lost there are some general differences as follows:

Phenol formaldehyde is always relatively dark in colour, usually dark orange, tan, brown or black.

Urea formaldehyde is usually lighter than phenol formaldehyde, often yellowish-white, a bit softer, and was a popular 'fake ivory'.

Melamine formaldehyde is usually quite a bit lighter, translucent, and harder.

Our feeling is that if it is phenol formaldehyde it is more likely to have been sold under the Bakelite tradename, if it is urea or melamine formaldehyde it is more likely to have been sold as Catalin, but at the end of the day the names are virtually interchangable!

2. What plastics are used for 'Hong Kong' (soft, carvable) and 'Taiwan' (hard, 'porcelain' like) Mah Jongg sets?

Well I have a typical Hong Kong export set to hand and I can tell you without a doubt it is high density polyethylene (tradename 'Polythene'). A very soft, almost waxy, thermoplastic material... cheap and nasty really! Probably the most common plastic in the world in one form or another.

The harder, denser ('heavier') sets with the 'porcelain' like feel are probably made from polystyrene. Also a very cheap thermoplastic material, but gives a harder, smoother finish, brittle in thin cross sections, but ideal for chunky Mah Jongg tiles! Yes, it is the same material as the expanded polystyrene chips and packaging, but in a much denser form.

The tile on the left, going by what Dr. Mike writes, is made of polystyrene. Harder, denser; reminiscent of ceramics.
The 3 tiles on the right are made of high-density polyethylene. Slightly translucent; reminiscent of soap or wax.

A third plastic which could be used for Mah Jongg sets is polypropylene, this would result in something a lot like the polyethylene sets, but probably a bit denser ('heavier'). To make life even more complicated polyethylene and polypropylene can be blended to make a plastic with hybrid properties.

These plastics can be virtually any colour imaginable.

To distinguish between these plastics you really need to burn a tiny piece... not what most of us want to do to our Mah Jongg sets! If it burns with a smokey flame it is polystyrene, if there is virtually no visible smoke it is polyethylene or polypropylene. BURN OUTSIDE and DO NOT INHALE FUMES.

Hope that answers your questions, if you've got any other queries on plastics then let me know.



Name: Tom Sloper
Email: tomster[AT]sloperama[DOT]com
Date: 18 Jun 2003


Hello Benjamin (jojinyoung) - long time no see! You wrote:

>Within a one week timespan I recieved two new mah jong sets. One from Taiwan, the other from Florida. The Taiwan set is triple layered, white, clear, clear, with a lovely cloth pattern between the two clear layers. It is the current fashion in tiles my friend assures me. The set from Florida is also triple layered, white, clear, and green. My question is this, after reading the faq on what tiles are made of, I am still unsure. Could these modern tiles also be a kind of acrylic?

Yes. They could. Although at one time (twenty years ago) I was a model maker who worked with several types of plastic (see ), I was not yet a devotee of mah-jongg, and I never did become intimately familiar with all the types of plastic in existence. The clear part of your mah-jongg tiles probably is, indeed, acrylic.

>Are the plastics in the FAQ able to be made clear as glass?

No. I don't think that the types of plastic described by "drmike" in FAQ 7c3 can all be made clear like acrylic.

>Oh! I also was at a foreign language workshop recently held in Oklahoma City. They had a little diddy on mah jongg games. I was glad to be able to share with them your website, which is the best in the world.

Aw, shucks! m(-_-)m Too bad you're not here in the Los Angeles area. My classes in mah-jongg are set to take place next month at the Pacific Asia Museum in Pasadena!


And another type of plastic is casein. Someone posted a question about casein sets on the Q&A Bulletin Board and I just kind of shrugged. Then there appeared this...

Name: gina
Email: gtsgfs at
Date: 04 Aug 2003


Looked up casein plastic for you Tom It is C 1930-1940. See samples here [DEAD LINK REMOVED 10/1/2020 - SEE FOR EXAMPLES]

on another site, I found information on this vintage plastic (used c 1930-1940)

Casein formaldehyde is a plastic of natural protein origin made from organic substances such as milk, horn or vegetable products such as soy beans, wheat and the like. It was obtained in 1897 by Adolph Spitteler and W.Kirsche who started out with whey and formaldehyde and tested the action of an enzyme on them. The patent was registered in Baviera and then extended to the USA, Great Britain and Italy. It should be noted that with its commercial name, Galalith (Galalite in Italy and Erinoid in Great Britain) it sometimes looked like celluloid, sometimes ivory and sometimes artificial horn. The first factory to manufacture it was in Great Britain in 1913. In 1930 world-wide production had reached 10,000 tons. Casein formaldehyde was used to make buttons, pins, cigarette-cases, fountain pens, umbrella handles and radio cabinets.

It would be surprising if this set was made during this time period. Hope this helps.

Name: Tom Sloper
Email: tomster[AT]sloperama[DOT]com
Date: 05 Aug 2003


Hello gina (gtsgfs), you wrote:

>Looked up casein plastic for you Tom

Wow, thanks, Gina! I'm going to add the information to FAQ 7c3.

>It would be surprising if this set was made during this time period.

Yeah, I agree. I tend to think that my 3-layer tiles are acrylic (at least the middle layer), or maybe polyethylene (at least the outside layers). A later plastic. Not pre-WWII.

As I recall, the domed cockpit canopies on the P-51D Mustang were made of plexiglas (which I think was acrylic). So I imagine that acrylic may have been kind of new before WWII but common afterwards. Oh - and, inspired by your post, I found some info on polyethylene at - Guess I'd better add that as a link in FAQ 7c3 too.

Thanks again, Gina - Tom

Gina Smith also sent information in response to a post on our Q&A Bulletin Board about a plastic called Alite .

Name: Tom Sloper

Date: 16 Sep 2003


Hello Elaine (gammalain), you wrote:

>I recently purchased a Mah Jongg set at a garage sale and would like to know approximately how old it is. It is called "The American Beauty" and is made of "Alite".

Sorry, I'm not the guy to ask about particular sets like "The American Beauty." You probably ought to take a look at Jim May's online mah-jongg museum (see FAQ 4a, above left). And I'm sorry, I never heard of "alite." I have an FAQ on plastics (it's FAQ 7c3) but alite isn't listed.

>although [the tiles] look like new, when they discolor, how should I clean them?

Gina wrote:

Alite is a vintage plastic that made up the American Beauty set by Royal Depth Control , manufactured and distributed by Crisloid Products, probably in the late 60's early 70's or even a bit later.  It came with eight jokers.  I have attached [a] picture... of a set that I sold about 2 years ago.  And I haven't seen one since. 

You can clean the tiles by taking a lightly damp cloth and wiping them, very lightly over the painted areas, and drying immediately.  Do not rub.  If there is goo, there is a product called "Goof Off" [CORRECTION: "GOO GONE"] that I have used that will removed sticky stuff but not the paint.  I usually get it on the internet. 

P.S. If the tiles are discolored from oxidation, as with all vintage plastics, you cannot change the color - the tiles have oxidized!


At the Game Developers Conference in San Jose, March 2004, I ran into an old comrade who collects and restores bakelite radios. Knowing this about him, I took the opportunity to ask him about bakelite vs. catalin. He told me that mah-jongg tiles are most assuredly catalin, not bakelite, since bakelite is rarely as light-colored as catalin.

Both materials are made of the same chemicals, but the difference is mainly in the process. Bakelite is made from powder, which is pressed into a hot mold under pressure. Catalin is made from liquid and poured into a mold.

Catalin tiles, my friend told me, started out white and yellowed with age. The information he gave me about cleaning and restoring bakelite and catalin are given in FAQ 7o .

Not all yellow tiles are Bakelite/catalin. If the tiles are highly reflective with rounded corners, then they're molded Bakelite/catalin. But if they are flat/matte with sharp corners, they may be casein which has been cut into shape. I have some sets of yellow tiles that were cut into tile shape, and I'm not sure, but think they're casein.

And you can learn more about bakelite and catalin at (thanks to aurelio247 of the eBay MJ group). There used to be an article at, but my old link no longer functions. For more info on the history of bakelite, see

Good information about catalin vs. bakelite at CoolOldGames:

Was "Olive Oil" Bakelite an intentional or accidental discovery?

On Saturday, May 27, 2023 at 06:28:16 AM EDT, Mia K wrote:
Olive Oil tiles
Hello Tom -
So grateful for your site and for the wealth of knowledge you share!
I can’t seem to find an answer to my question…which is about vintage Olive Oil tiles that are semi-translucent (and glow green under bright light). Was this an intended feature, or an accidental side-effect, or ? Thanks, I’ve always wondered!
Sent from my iPhone, which often confuses "o" and "i"

囧 I'm sorry, Mia, but I don't know. You might assuage your curiosity by reading up on Leo Baekeland, the inventor of Bakelite, and Union Carbide and Carbon Corporation, which bought his invention from him. A quick Google search gave me these resources:


    I don't know any details about Baekeland's invention process, what mixtures didn't work and what mixtures did work, nor do I know whether the "olive oil" looking plastic was found asymptotically or intentionally. From what I've learned about inventors, I imagine they try a lot of things to find a few solutions that work well. For instance, Thomas Edison tried over 6,000 filaments in order to pick the perfect one that would glow well and last a long time. (Found that wording via a Google search too.) So, was the tungsten incandescent bulb intentional or serendipitous?

    I don't have any "olive oil" tiles in my collection. I have seen "applejuice" tiles, which are similar only with less green in them. I wish you'd sent a picture along with your question!
    Good luck with your quest. Maybe you'll find more details about Baekeland and Union Carbide, and when/how he/they came up with that olive oil mixture. Or maybe olive oil plastic was produced by the American Catalin Corporation or the Bakelite Corporation. Sorry that I can't answer your question for you. I'll append this exchange to FAQ 7c3, where there are other discussions about the plastics mah-jongg tiles are made of.
    Play safe out there. And may the tiles be with you.
    Tom Sloper
    Rochester, New York, USA
    May 27, 2023
    Donations appreciated

    Regarding the mysterious substance called "Chinese Bakelite"

    >From: gina smith
    >To: mj@sloperama
    >Sent: Sunday, March 11, 2007 9:39 AM
    >Subject: from gina
    >OK, Chinese Bakelite vs "real" bakelite.  If you break a Chinese Bakelite tile in half,  the interior is stark white and fractures kind of like a charcol briguette.  When tested for bakelite, the white plastic (and I have no idea what it is) doesn't test positive.  It seems that there is some kind of matte paint finish on it.  I can remove it with nail polish remover.  You won't get any of this on a "true" bakelite tile. You may get some color change of the exterior of a "true" bakelite tile due to oxidation (?) or age, but the interior is still the same color as the day it was made.   Can;t find any other information about Chinese Bakelite tiles.  The carvings in the older sets are usually highly detailed.  Most likely hand done. 

    Chinese Bakelite: what kind of glue?

    From: "Jay Davis" (jmd5)
    Sent: Monday, April 21, 2008 11:48 AM
    Subject: Mah-Jongg Q+A
    > My mah-jongg question or comment is: Hi, I have a set of chinese 
    > bakelite tiles with thin translucent green backs. Quite a few of the 
    > backs have come off and I would like to know what kind of glue I 
    > should use to reattach them (I was hoping to use something that would 
    > not show through). Thanks! Kim

    Hi Jay,
    I'm not sure what your tiles are made of. The term "Chinese Bakelite" is apparently one that was coined recently by sellers of older mah-jongg sets, and since it's a made-up term, there's no dictionary where anyone can look up the term and see which kind of plastic that really is. And even if everyone agreed that "Chinese Bakelite" is the same thing as "yellow casein," there's no way I could be positive that you knew for certain that your tiles were yellow casein.*** [See Oct. 1 2020 update, below]

    So, since I'm not sure what kind of plastic your tiles are made of, I have to give a generic answer. Modern plastics like acrylic and polyurethane are best glued together with solvent (which you could get at the plastic store, where they could furthermore look at your tiles and confirm which solvent is right for your plastic). But it's likely that your tiles are made of a formaldehyde-based plastic, and I don't know about the backs (those might be an acrylic, or another formaldehyde-based plastic).

    So I think you probably want to use "superglue." It's clear. But like Peter Gallagher wrote in FAQ 7o, use it sparingly for best results. Also, unless you buy a slow-drying variety, act quickly after applying it to align the pieces, otherwise they could get stuck together improperly aligned.

    May the tiles be with you.
    Tom Sloper
    Author of "The Red Dragon & The West Wind," the definitive book on mah-jongg East & West.
    トム·スローパー   /   湯姆 斯洛珀  /  탐 슬로퍼
    Los Angeles, CA (USA)
    April 21, 2008

    *** Update, 2020: I used to think Chinese Bakelite was really casein, but now I'm thinking it might be polystyrene. See the polystyrene "red five" tile in the image above. Polystyrene tiles are not shiny, and have a similar feel to so-called "Chinese Bakelite." Reminiscent of ceramics more than soap or wax, as Dr. Mike wrote.
    - Tom Sloper
    October 1, 2020

    Useful link: was created by an anonymous collector of vintage Mahjong sets. The section about history, identification and restoration of vintage plastics is well done. Some plastic ID tips from that site:

  • if it floats in water, it is either polyethylene or polypropylene
  • if it has a metallic "clink" it's probably polystyrene
  • if you are willing to burn some of it with a soldering iron or match, you can get a lot of information. Texloc has a great chart covering most of the modern plastics and some of the vintage plastics.
    (Thanks to "Nath Krismaratala" for the link.)

    >Name = Amelia F
    >Date = April 8, 2005
    >Comments = I've recently seen some newish tiles for sale that are called "Marblette". They're white, some kind of plastic, and I wonder if anyone knows when they were made or anything else about them. Are they the same as Alite?

    Hi Amelia,
    I'm sure this has been discussed before, but I didn't see anything in FAQ 7c3 when I looked just now. I did a quick Google on marblette and it looks like this is just a brand name for the same kind of phenolic plastics as bakelite and catalin, made by The Marblette Corporation, which I assume has gone out of business some decades past now. Lots of info out there if you just use Google.
    Tom Sloper

    Los Angeles, CA (USA)
    April 8, Year of the Rooster

    Tile materials not mentioned must be undesirable?

    >From: dhen
    >Sent: Monday, July 14, 2008 11:13 PM
    >Subject: lucite mah jong sets
    >Hello Tom,
    >I was curious, in your FAQ on different types of Mah Jong sets you didn't mention
    >lucite or bakelite. Are these less desirable as sets?
    >thanks, Pescadero10

    Hello dhen,
    The desirability of a set has no corollation whatsoever with whether or not its material is mentioned in my FAQs.
    You're right that I didn't mention Lucite. Sure, there are sets that use Lucite as the material (or as one of the materials). I'm sure there are lots of materials (especially the numerous plastics) that I didn't mention. Guess I could add that to FAQ 7c3 (the discussion on plastics)...
    And I most definitely do discuss Bakelite in the FAQs. Were you only looking at FAQ 7a? FAQ 7a isn't about material - FAQ 7c is about material. FAQ 7a is about "types" of sets (which kind of mahjong a set was made to play, and which market the set was made to be sold in).
    May the tiles be with you.
    Tom Sloper
    Author of "The Red Dragon & The West Wind," the definitive book on mah-jongg East & West.
    トム·スローパー   /   湯姆 斯洛珀  /  탐 슬로퍼
    Los Angeles, CA (USA)
    July 15, 2008

    Celluloid, part 3

    > From: Dave G
    > Sent: Sunday, April 21, 2013 5:44 AM
    > Subject: Link to scholarly discussion of the care of celluloid / French ivory (quote indicates how French ivory was made)
    >[DELETED] Full text is available here: [DELETED]

    Thanks for the link, Dave. I wasn't sure how much of the text of your email was copied and pasted from that site, so I played it safe and deleted it all.
    May the tiles be with you.
    Tom Sloper

    Creator of these Mah-Jongg FAQs -- donations appreciated.
    Author of "The Red Dragon & The West Wind," the definitive book on Mah-Jongg East & West.
    Los Angeles, California, USA
    April 2, 2013

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