It might suprise you but the overall hardness of a table tennis rubber has a lot more factors to it than you might think. Manufactures tend to give a degree rating in terms of sponge hardness for example 45deg or 50deg and thats it. While this is a very important metric they do not give you any information about the rubbery bit that sits on top of the sponge – the Topsheet. Seeing as this is the bit that actually makes contact with the ball you would think they would give you more information! So I have written this article explaining in detail the factors that contribute to overall rubber hardness.
So there are 4 main factors that can influence how hard or soft a rubber feels:
1) Sponge Hardness
Sponge hardness is probably the most influential factor in how hard a table tennis rubber feels. This sponge density is measured by what’s called the shore scale which is a measure of hardness. Most Manufactures use Shore O scale whereas Butterfly and DHS use the Shore A scale. Sponges with a lower degree of sponge hardness (e.g 35deg) will feel softer and sponges with a higher degree of sponge hardness (e.g 47.5deg) will feel harder.
Table tennis sponge hardness can vary from 32.5degs (Tibhar Nimbus Sound, Gewo Proton Neo 325) all the way up to 55degs (Xiom Omega 7 Tour) and beyond in some cases depending on which shore scale different companies use. Harder sponges give you a higher potential for speed (max speed) but also give you less feeling and control whereas softer rubber it is the reverse. Softer have much more control but can ‘bottom out’ which means past a certain effort point output effiency decreases – the harder you swing is not proportional to the extra speed you get out of it. This is why pros use harder rubbers, to get more speed.
Sponges with a higher Shore rating will be denser, harder to compress and feel harder. Sponges with a lower Shore rating will be less dense, easier to compress and feel softer. Sponge hardness is normally stated on the rubber packet so its nice and easy to tell how hard a sponge will be on a rubber. However this is the only piece of information they give you. Everything below is not disclosed, which is why sometimes its tougher to choose a rubber than I feel it needs to be.
2) Topsheet Formula
The topsheet formula is the chemical make-up of the topsheet rubber and pimples. Some manufacturers use more natural sources of rubber and others use a more synthetic and this has an effect on the way the rubber feels. Butterfly in particular use a much more natural rubber formula, which is probably partly why is more expensive than other table tennis rubbers. DHS on the otherhand use a much more synthetic formula which can make the rubber surface feel artificial and plasticky – this is much cheaper to make though hence why Chinese rubbers are cheaper.
Natural rubber gives a much more soft and pleasant feel. Which is why Butterfly rubbers in general tend to feel quite soft despite their hard sponges. DHS rubber topsheets on the otherhand have a very hard and less flexible feel. Some people describe it as feeling like a brick! But each approach has their different advantages but ultimately one of the main reasons why for example Tenergy and Hurricane 3 feel so different, despite having fairly similar sponge hardness’s, is down to the chemical formula of the rubber.
3) Pimple Structure
The pimple structure of a rubber is very important to how a rubber plays. There are 4 dimensions to a pimple structure: Pimple shape, Pimple height, Pimple width & space between pimples. Changing any of these dimensions change both spin and speed characteristics of a rubber and also just as easily how hard a rubber feels. The Butterfly Tenergy series is a beautiful example of the power of the pimple structure.
Butterfly have named the Tenergy series after the pimple structure code for each rubber. e.g 05, 64, 80 & 25. The interesting thing about the Tenergy rubbers was that each different rubber had the same sponge and the same sponge hardness. Despite this the rubbers felt quite different to one another and performed differently for various shots. Tenergy 05 has a harder feeling and is selected by people who prefer to loop whereas Tenergy 64 has a softer feeling and is selected by people who prefer to flat hit. This is the pimple structure in action.
Butterfly have a great info graphic to demonstrate the pimple structure they used for each rubber.
So back to hardness. Pimple structures can change how soft or how hard a rubber feels by a number of ways. Pimple structure density is a big one. If there is less space between pimples and the pimples are wider and shorter the pimple structure is more dense and there is less flex in the topsheet creating a harder feeling. An example of the Tenergy series is Tenergy 05 which has a harder feeling of all the Tenergy rubbers even though the sponge is the same. if there is more space between the pimples and the pimples are narrow and long then the pimple structure will be less dense and the topsheet will have more flex and the rubber will feel softer. And example of the Tenergy series would be Tenergy 64 which has a softer feeling than the other Tenergy rubbers despite having the same sponge.
Bottom line is that rubber with a less dense pimple structure will feel softer than a higher density pimple structure on the same sponge. This is how some rubbers despite having very hard sponges I.e. 50deg can feel much softer overall than other rubbers with a softer sponge but a very dense pimple structure (Tibhar Quantum and Tenergy 64 are good examples of these, both having near 50 degree sponges but can feel softer than other rubbers with a 45 deg sponge)
Soft feeling pimple structure: Narrow, long pimples with large spaces between pimples
Hard Feeling pimple structure: Wide, short pimples with small spaces between pimples
4) Topsheet Thickness
Different rubbers have varying thicknesses of topsheet, the surface rubber that contacts the ball.
This aspect of the table tennis rubber has come into the forefront recently as lots of manufacturers are experimenting with thinner topsheets. I feel this a promising technology but thinner topsheets have been around before.
The Joola Rhyzer series is an example of a newer generation rubber using this technology.
By having a thinner topsheet it allows the topsheet to mould around the ball a little bit better and provide some more flexibility to the rubber. This added flex can make the topsheet feel a bit softer as the ball penetrates through the rubber into the sponge easier. Examples of rubbers with a thin topsheet include: Joola Rhyzer, Donic Bluestorm, Andro Rasanter, Aurus Prime/Select & Xiom Omega 7. These are all newer generations of rubber and certainly have advantages but generally feel a lot softer than there sponge hardness would suggest. For example Rhyzer 48 almost feels like a 45deg rubber.
Rubbers with Thicker topsheets do not have as much flex in the surface rubber and as a result feel a lot harder as the ball doesn’t penetrate the rubber into the sponge as much. Examples of rubber with a thicker topsheet include: DHS Hurricane Neo 3, Yinhe Big Dipper, Nittaku Fastarc G-1, in-fact most Chinese rubbers tend to have a thick topsheet.
I hope I have provided some extra clarity on overall rubber hardness and hopefully should explain why certain rubbers are softer or harder than they appear from the sponge hardness. As you can see there are multiple factors that affect how hard a rubber feels and ultimately these same factors can have a big impact into how a rubber plays. I will explore how these factors affect game play in later articles.