On tacky rubbers

We’ll discuss tacky rubbers and answer the necessary questions of how tackiness can be defined, how it’s created, how it works and finally how to apply it in table tennis.

[Disclaimer] Wall of text. Please read the questions by its given order, because we use derived points from previous questions as arguments for the following ones.

0. Motivation

1. What’s the difference between a tacky chinese rubber and an european rubber?

Before we start exploring the tackiness phenomenon, let’s get rid of some inexact terminology first.

Sometimes people attribute the term tacky or sticky exclusively to chinese rubbers while nontacky rubbers are called european. However, there are tacky european rubbers (rubbers manufactured in Europe) and tacky chinese rubbers (rubbers manufactured in China/Asia). This holds true for their nontacky counterparts. Hence this distinction doesn’t help us and won’t be used in the future.

Hence a tacky / nontacky rubber will be called tacky / nontacky independently of its manufacturing location but based on its actual properties.

We now used the term “tacky” many times without thinking too much about it. Let’s change this with the following section.

2. What’s tackiness?

Tackiness or stickiness, just as you know it from a regular glue describes the ability to hold (stick) two things together. In our table tennis case we want to stick the ball to the topsheet for a short time.

You can test this with a sheet of paper. Press your rubber against the paper and see if you can lift it. If true, you hold a tacky rubber in your hands. If the stickiness is really high, you can even lift a table tennis ball this way. A nontacky or grippy rubber won’t lift anything.

The next interesting question might be, how this stickiness is achieved, i.e. how can the rubber hold the ball anyway?

3. What makes a rubber tacky and how does it work?

Remembering the article on rubber chemistry, we know that the rubber consists of long polymers. We imagined them as long chains and in the boosting case we saw that we wanted to stretch them.

We made a short remark on entropic elasticity. These bulky words just say that a polymers chain would never stretch itself. On the contrary it wants to clew itself to a fuzzy ball.

The reason for this goes back to the second law of thermodynamics, which roughly says that the disorder of all things in the universe increases. The measure of this disorder is called entropy. The next time you have to clean something just remember, the universe doesn’t want it properly arranged and clean anyway ;).

Back to the rubber. If you stretch the rubber it’s entropy(or disorder) is lower compared to the fuzzy ball state since all molecules are lined up. Hence, as soon as you let the rubber go, it will return to its fuzzy ball status. Because you can view/call this behavior elastic, we finally arrive at the term “elastic entropy”.

So, how does this help us with our tackiness problem?

A grippy rubber creates its friction simply by rubbing the straightened polymer chain mesh against the balls surface. You might think the ball is smooth, but with a good microscope you can see that the ball rather looks like you “tried” to make a ball made of cellulose strings woven to a ball-like form with many gaps and uneven areas in between. Rubbing the two rough surfaces of the ball and the grippy rubber together creates the friction to handle incoming balls.

On the other side, the tacky rubber goes a step further. The manufacturer willingly breaks some polymer chains. The rubber surface then looks like some kind of dry mop.
These limb polymer chains doesn’t seem to help at first sight. However, if we hold one end of the chain and increase the temperature we get an interesting result.

Remember at first that the temperature is roughly defined through the average movement speed of the air particles. This high speed molecules collide with our limb chains and pass them some energy through their impact friction and hence heat. The rubbers polymer chains now have some extra energy. Remembering the second law of thermodynamics we know how this energy is spend. The chain start clewing itself to a fuzzy ball.

Depending on which chain length you use and how much heat is applied, we don’t necessarily reach the fuzzy ball state, but might stop at the point where the free end minimally clewed itself to some sort of hook.

Now remember how we described the surface of the ball, as a fuzzy ball of cellulose string with many holes. This combination makes a perfect hook and loop mechanism, doesn’t it? The same principle is used for hook and loop fasteners (or velcro fasteners) for shoes and other materials like all sorts of velcro games ;).

To state it again, the underlying reason which makes a rubber tacky is the hook and loop mechanic between the half loose polymer chains of the topsheet which are partially clewed and the rough surface of the ball.

Sadly this hook and loop mechanism isn’t picky and likes to grab dust particles just like balls, so we have to clean the rubber more often.

Now we might wonder:

4. If tackiness is such a good thing, why aren’t all rubbers tacky?

The table tennis rubber has to achieve many different things. At first you want to stop the ball from slipping at contact, you want some sort of grip wether it be based on normal friction or hook and loop techniques. After that the rubber deforms and stores the incoming energy(speed+spin) and then stretches back into its normal position. By doing so, all the via deformation stored energy is released and we return parts of spin and speed onto the ball.

Nontacky rubbers are done at this point, the ball leaves the blade. For tacky rubbers the situation is a bit different.

Remember the hook and loop design. The ball is still entangled with the hook from the polymer chain. To overcome this, it has to spend (lose) some of its energy in terms of speed and spin.

In particular this means that – given two identical rubbers beside the tacky/nontacky difference – a nontacky rubber generates more speed and spin because it doesn’t lose energy on the way by the need to break the hook loop mechanism apart. Here‘s an old paper where different! tacky and nontacky rubbers were tested.

Now another question might occur:

5. If tackiness reduces spin and speed, why aren’t all rubbers nontacky?

There are certain situations during a game, where you might want to trade the additional spin and speed for others things.

Example 1 : Countertopspin close to the table

If we counterloop close to the table, the topsheet experiences a high amount of force. It has to reverse the incoming rotation in the opposite direction. Because we counterloop so close to the table, the incoming loop likely carries a high amount of spin and speed. This forces us to hit the ball very thin on its upper side if we want to bring it back on the table. This combination makes it very probable that the strongly spinning ball isn’t catched by the rubber and slips through.

Imagine a fast spinning standing ventilator. If one would try to stop it by pressing the fingers against the rotating blades without applying to much pressure, he would be likely to fail. However, if he uses a some sort of hook on a string and slightly hold it into the rotating blades he is more likely to catch the blades, especially if he could use several hundred as in our table tennis case.

In this case we saw why we traded a bit of speed and spin for a higher chance to actually be able to return the ball. A returned ball with less spin and spin is still better than a ball which slipped through and didn’t even reach the other side.

Example 2 : Short receive

As the receiver, we usually try to avoid giving the opponent attackable balls. To prevent this, we try to return the ball very short, sometimes call drop shot.

Since the tackiness reduces the speed and spin, tacky rubbers are exceptionally good at producing spinless and short drop shots.

Additionally, there are some side effects which are worth being discussed.

Imagine to receive a short backspin serve.  We don’t want to make a dropshot out of it but produce a backspin ball.

Higher rated player usually play harder rubbers, especially on the forehand side. This means, we’re unlikely to activate much of the sponge of our hard rubber for the incoming slow backspin ball. Coupled with the reduced speed and spin potential, we’re likely to experience a ball pushed into the net because of the high stickiness or a ball which pops up, because we weren’t able to generate enough spin to overcome the incoming spin and to add our own.

Hence a tacky rubber receiver has to push really hard into the ball to get a high quality push return. This can be observed on almost all chinese players. If they receive with the forehand side, it’s almost exclusively a dropshot or a push with a visibly strong slicing action.

Gladly the stickiness prevents that the ball goes too long by pushing so hard.

As a side note, let’s state here that the energy loss in the vertical direction (speed) is greater than the loss in the tangential direction (spin). This means, the ball loses more energy in a normal bounce test (doesn’t reach many rebounds) compared to the test where you spin the ball up in the air with a pushing movement and catch it with a blade angle which reverses the spin.

The stronger energy loss for the ball speed is the reason why chinese players with their tacky forehand rubbers switch to their nontacky backhand for smashing high balls.

Since they hit the ball centrally and not tangentially, the energy loss would be too great with the tacky rubber.

We’ll later discuss the remaining stroke types, but for the moment let’s move on to another question.

6. Why are tacky rubbers rarely used on the backhand side at the professional level?

At first let’s think about which stroke types are common for the backhand side on a sufficiently high level.

After the over the table receive either the weak return is attacked with a full swing or – incase of a strong return – some sort of spinblock is used. A bit further from the table the usual counterlooping happens.

Let’s start with the receive.

Based on our spin evasion article, we know that almost any ball can be looped with a backhand over the table loop by either overpowering the incoming spin or evading it. Because it requires much footwork and exposes us to an open side, our attack should be well placed and strong. Since we mostly avoid the spin (hitting where the ball doesn’t spin) we don’t need a super thin contact and the topsheet doesn’t experience high forces. Hence we don’t really need the tackiness here. We just lose much speed and a bit of spin if we use a tacky rubber on the backhand for receiving.

The next case is blocking a strong incoming loop. At first the tackiness sounds good here. However, the lacking speed might force us to play more passively and enables an opponent to lock us down on our backhand side. Over the long run he would simply overpower us.

Finally, the counterloop.

An counterloop might be used against balls from the opponents backhand or after he stepped around to use his forehand. The backhand balls carry less energy than full forehand swings.

We get two cases. Case 1 where both players play nontacky and case two where we play tacky on our backhand.

Case 1 – Opponent starts looping with his nontacky backhand into our nontacky backhand

Because we want to counterloop and the ball carries much spin, we need to make a thin contact. Sadly we just got a nontacky rubber and are thus susceptible for the ball to slip through. This can’t be changed and partially explains why the backhand loop to the backhand side is such a strong option for high skilled players. It forces the receiver to either be passive by blocking or risking to miss the ball if he counterloops.

Case 2 – Opponent starts looping with his nontacky backhand into our tacky backhand

Now we don’t have the problem of the ball slipping through we can attack confidently. However, the ball might carry enough spin but less speed and a high level opponent could use this time to step around and proceed to lock us on our backhand side. But if he continues to use his backhand, he now faces the problem of attacking a ball with much spin with a thin contact and is susceptible for ball slipping.

Time for another question:

7. Is a tacky or a nontacky rubber better for looping backspin?

Given that you perform the correct stroke, i.e. that your bat has the necessary speed to prevent to ball from dropping down upon contact it’s just a matter of the blade angle.

Since we have a lack of speed in tacky rubbers, the stroke must be made slightly forward with a contact point above the balls equator. A nontacky rubber doesn’t lack this forward speed and we can just swing upward and hit at the equator of the ball.

Even more precise, for slow backspin balls it’s a matter of the correct blade angle. However, the faster the push the less options we get to variate our loop. This holds especially true for nontacky rubbers.

Given that amateurs are often late to the ball and do minimal wristy upward strokes from a hollow back it might be easier for them to use nontacky rubbers to loop backspin.  A tacky rubber which is used that way won’t pass the net because the forward speed is missing.

To sum it up, a nontacky rubber is easier for looping backspin if you’re caught off balance but limits your options in terms of the possible placement length. For very thin contacts you also have a higher change to miss the ball due to slipping.

Let’s discuss another often occuring question:

8. Are tacky rubbers more affected by incoming (side-) spin during the receive?

From a technical point no, even contrary. Given otherwise identical rubbers, the tacky rubber produces less speed and spin as previously mentioned given the same incoming spin. This means that a tacky rubber technically reacts less to incoming spin. The difference between incoming and outgoing spin is bigger for tacky rubbers.

Now the question remains why many intermediate players – based ontheir experience – think overwise.

The reason lies in the layman perception of spin affection and the difference to the technical point of view. The layman just imagines two different paths of a sidespin ball and says that the earlier curving ball must be more affected by spin. However this earlier curving is due to the lower forward speed of the tacky rubber and has nothing to do with the outgoing amount of spin.

Since many amateurs have trouble against sidespin and given  their point of view or interpretation of spin affection they’re indeed right to say it’s harder to receive sidespin with a tacky rubber.

Finally, the last question before summarizing the whole article.

9. Are tacky or nontacky rubbers better for intermediate players?

Let’s start with the backhand. Nontacky rubbers provide an easier sidespin handling but backspin balls might go long. Given that the opponent is intermediate aswell, this shouldn’t be a problem.

Attacking might be better with nontacky again, we don’t have to fear intense close to the table backhand counterlooping rallies with the danger of slipping, just some sort of punchblocking/hitting battle. Lifting backspin while being late to the ball is easier with nontacky rubbers as mentioned above. Only the block is supposed to be better with a tacky backhand for amateurs.

Now the forehand case.

Given that most amateurs have trouble at truly brushing the ball, tacky rubbers give a higher security to hit the other table half even if they hit nearly through the ball. The receive is easier with nontacky rubbers regarding sidespin and backspin, the most common amateur bottlenecks.

Blocking might be easier with a tacky rubber on the forehand side as long as the attacker has sufficient spin and speed on the ball. Weak balls are easier to block with a nontacky rubber.

Counterlooping/Looping might be easier with tacky rubbers – given that amateurs hit more than they brush and hence they don’t need to fear overhitting with tacky rubbers.

Depending on the individual strengths and weaknesses of the developing player in the above mentioned categories and the outlook on his future development he might chose accordingly between tacky or nontacky on the forehand side.

Lower level players with a rather poor outlook on improvement over time due to whatever reasons should definitely look for a nontacky rubber on the forehand side.

10. Summary

Tacky rubbers are neither chinese nor european, this just describes where they were produced.

Tackiness or stickiness means the ability to hold two things together, here the table tennis ball and the rubbers topsheet at extreme angles.

This is achieved through a hook and loop mechanism of partially free rubber polymer strings which form hooks by using environmental heat. This hook then catches the fuzzy cellulose ball and provides a better chance to catch the ball in general.

The bond has to be broken once the ball leaves the rubber which costs some energy in form of much speed and a bit of spin.

Tacky rubbers are especially good at receiving short, the first attack and counterattacking with the forehand side, while being demanding at the same time in terms of a proper technique and the basic understanding of the game.

Hence the recommendation to use nontacky rubbers for amateurs, nontacky rubbers for intermediate players with the option to upgrade to a tacky forehand as a long term investment and finally the tacky forehand plus nontacky backhand combination of (semi-) professional players.

EOF :).

 

 

 

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14 comments on “On tacky rubbers

  1. Greetings 🙂

    Much needed article elaborated accessibly – this is a very good article indeed. My father is a chemical engineer who also played a bit of high school level table tennis and he gave an explanation on tackiness in the same fashion. However Ive always been curious as to the possibility of “adding” tackiness. Sticky film protectors can help taking the dust off of the rubber and maintain tackiness, however the tackiness is not added. Years ago I successfully added tackiness to a rubber, but the story was rather complicated. I had a DHS skyline III which i tuned with an oil I can’t recall, i then proceed to, out of curiosity, taped double sided tape onto the topsheet. I left it like so in hot and humid thai climate and then once I removed the tape the topsheet became tacky! I have never done that again since but heres my quetion:

    is there any possibility to add “tacky” glue/ material onto the rubber?
    additional question: can heat and humidity ruin tackiness (i once heated the topsheet with a blowdryer and the topsheet just dried up, and playing in humid and cooler [24c] seemed to have made the surface slippy at least temporarily).

    Thank you so much for the article – hope to read more from you soon!

    • Hi Ephemeral,
      the following is just my laymen understanding of chemistry, so you still might want to ask your father for a professional explanation.

      @protectors: Rubber protector sheets prevent air from reaching the rubber surface and thus slowing down the exchange of sulfur links with oxygen ( which degrades the rubber, it becomes less elastic/brittle ).
      Nontacky protectors are used for tacky rubbers, since the rubber surface already sticks to the protector sheet because of its own tackiness. For nontacky rubbers you need a tacky sheet to properly stick to the nontacky rubbers surface.

      @adding tackiness: Of course you can add tackiness to a rubber. Beside the ittf-rule/legal problem, you’ll need a glue which can be evenly spread over the rubbers surface and generates an even tackiness level all over it. Additionally you need a glue which bonds with the rubber surface so you don’t produce a sticky ball and a nontacky rubber after a few points ;).Finally, the used glue needs to dry very slowly, or your tackiness is gone more or less instantly ( think of applying instant glue ). Your tape-experiment shows that its indeed possible to transfer some glue (of your tape) on your rubber. But again, the above quality concerns for your created ‘tack-layer’ might need further tests ;). The usual way rubber manufacturers / ‘rubber restorer sprays’ (atleast to my knowledge) add tackiness is using a rubber solvent (if you haven’t already, you might want to look at the rubber chemistry article). They trade a bit of topsheet elasticity for breaking some polymers (partially) free which then serve as tacky hooks for the ball. Because you can’t ‘tell’ the rubber solvent to attack only one side of interwoven polymers, you’ll sometimes get tacky rubbers which loose their tack quickly ( solvent broke most polymers free at both ends ) while others remain their tackiness for longer time (solvent mostly broke one side free) given the same circumstances.

      @heat: A certain amount of ambient temperature is necessary for your rubbers molecules to be elastic. Above a certain point, additional heat doesn’t add elasticity in the same amount as it decreases the tackiness or accelerates the rubbers aging process.
      For the aging process, remember that a rubber ages/gets worse by exchanging sulfur molecules with oxygen molecules. Now you bombard your rubber (by heat through room temperature or more extreme your blowdryer) with very high energy air molecules, which accelerates the aging. This means your rubber gets brittle/old faster and loses its tackiness, because the previously partially linked polymer hooks get brittle aswell and finally break loose.

      @humid condition: Think of the water molecules in the same way as dust particles. Although tacky rubbers attract and collect more dust than nontacky rubbers, they are better suited to overcome the water layer through the long rubber polymer hooks extending beyons the layer. So a tacky rubber is better suited to fight humidity and water itself doesn’t damage the tackiness in any relevant way because rubber and water hardly react to each other. That’s also the reason why you clean tacky or nontacky rubbber alike with pure water.

      I hope I have covered all your questions, if not let me know.

  2. Just curious, but you say that the tacky rubbers allow it to hook into the cellulose in the ball. Is this different now that the cellulose balls are being phased out? Does that change the calculus above?

    • Hi owenallenaz,

      as far as I know plastic balls have a smoother surface than celluloid ones. This of cource means that it’s harder to get some grip on them. Furthermore it’s harder to spin the ball and – because of the smoother surface – the spin on the ball doesn’t create much drag or lift, compareable to a smooth or pimpled golf ball.
      All this points helped tacky rubbers to gain some ground on the backhand (at the forehand side it’s standard for chinese pros). Because you need harder rubbers now to get the same spin you in particular need to hit harder into the sponge. The tacky surface helps you hitting more into the sponge without overhitting the table.

  3. Pingback: The best rubber to loop backspin | Thoughts on Table Tennis

  4. Pingback: Grippy vs. Tacky II | Kineske gume

  5. Interesting article specially for the beginners like me… I recently developed interest for the game of ping pong!

    However the challenge started two weeks ago when I decided to by new racket, tons of questions pops out

    which blade, rubber, sponge…. bla bla bla…. and the moment I figured them out, someone just informed me about tacky and non tacky rubbers…

    Wow!!! that made me again blank!

    Thanks to the wonderful writeup and explaining it to everyone….

    Now more confident that I should get tacky rubber for BH and non tacky to FH 🙂

  6. Pingback: Throw Angle | Thoughts on Table Tennis

  7. Excellent article, thank you so much for this! I feel very enlightened now. I recently have been getting into tacky rubbers and I thought it was because I was able to produce MORE spin, but I suppose it’s similar to the sidespin reaction concept where I have the illusion of more spin when it is really the lower speed that is creating that reaction. However, I think the tacky rubbers suit me well because of this, since I am one of those amateur players that hits through the ball too much. 😉

    It seems like there are a lot of misnomers in table tennis because a lot of concepts are based on subjective experience and feel. Perhaps something for another article or perhaps something you could sum up, I was curious about the concept of throw angle, how would you explain it from your more objective scientific view?

    • Hi Damon,

      thank you for your kind feedback, replies like this keep my motivation high :).

      I’m especially satisfied to hear that the article was understandable and helpful for someone, as you clearly demonstrated with your post :).

      As you’ve said, there a many myths in table tennis, aggregated over many years and repeated in various discussion boards a hundred times until they became some sort of false common sense or “false friends”. I continuously try to be the mythbuster while trying to explain where this false sense of understanding came from. You might look at the blade design,chemistry and floating balls article if you like such things. Somewhere I also explained the “kick” phenomenon which might be interesting to you aswell.

      The throw angle issue is on my ToDo list, but my articles are quite time consuming to research and write. Especially since you usually can’t find any similiar in-depth explanations for my most clicked topics on the internet, so I have to connect the dots manually and have to describe the resulting curve as layman friendly as possible.

      The throw angle issue is a complex issue because it basically asks for some research on the flight of the table tennis ball regarding the spin/speed ratio. In some paper I can’t remember at the moment I also read that the drag effect for topspin doesn’t scale as good as one might assume related to the energy you have to spend to increase the spin and thus recommended fast table tennis with moderate spin to be more energy efficient. However, I have to do the physical modelling myself and need to break it down to 10. grade physics afterwards and this will take some time as well. But as my current thesis adviser recently said on a mathematical issue:”If it would be easy to do, someone else would already have done it”.

      After this modelling, we can make some statements if “throw angle” is the right definition, if it’s a sign of the quality of a topsheet etc. pp.. But as long as no one dived into it, we’re left with “useless” opinions, sorted by their popularity in some discussion boards.

      So please stay tuned and suggest more topics you find interesting in the meantime :). -Yoda

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