A truly scratch-proof clear iPhone case doesn't exist, but a hard-coated clear case comes pretty close. The back of a case is usually made of a sheet of very thin, hard, clear polycarbonate. A hard coat is a protective coating that is cured onto the polycarbonate and strengthens the case. Polycarbonate is pretty soft because of its nature. Before the addition of a hard coating, it would rate around a 2B or HB on the hardness scale, which is pretty similar to the lead in a pencil. A harder coating would rate higher on the scale.
Despite the hard coating, the case remains susceptible to scratches. Sand and grit can still scratch the case because quartz is harder than the coating. Clear cases become hazy over time mainly because of many tiny scratches that scatter light.
This article explains the differences between 2H and 4H hard coatings and what kind of tests are performed to measure hardness. This information should help you evaluate clear cases better and help you understand scratch resistance.
Key Takeaways
- Scratch resistance in clear cases is usually rated by the pencil hardness test (ASTM D3363), where 9B is the softest and 9H is the hardest.
- Because uncoated polycarbonate (PC) is relatively soft, it was reported in a 2024 study in Progress in Organic Coatings that it has a hardness of 2B. The hardness was increased to 6H by the development of a laboratory-made coating.
- Hard-coated clear cases have a special coating on the clear PC case, which is cured by ultraviolet light (UV) and provides a surface hardness of 2H to 4H. Other, more advanced, lab coatings increase surface hardness even more.
- A 4H resists more everyday pocket wear than 2H, but no plastic coating can fully resist sand, which contains quartz.
- Pencil hardness results depend on how the test is done, so a "4H" claim from one brand is not always equal to "4H" from another.
To understand the difference between 2H and 4H hardness coatings, let’s explore why clear cases scratch easily.
Why Clear Cases Scratch Easily
Clear cases, like much safety equipment and eyewear, are made with polycarbonate (PC) to provide impact protection, as PC is very difficult to crack. PC can, however, scratch relatively easily.
One scratch does not diminish a case's protection or makes the phone difficult to see. It is only when several scratches occur that light scattering makes the case appear foggy and difficult to see through.
In the case of a protective case cover, there are two types of damage: abrasion and gouging.
- Abrasion is a kind of damage that happens from regular use that slowly dulls and clouds the case. It is caused by dust in pockets, office desks, and other abrasive surfaces.
- Gouging is a single, deep scratch from sharp objects that cut into the case.
It is important to reinforce case covers with hard coatings to counteract damage from abrasion. These coatings do very little to protect a case cover from a gouging scratch, however.
Understanding the Pencil Hardness Scale
Here's the method used by experts: a pencil lead is held at a 45-degree angle and pushed across the surface. Testers usually start with a hard pencil and work the grades until one no longer marks or cuts the coating. That grade is the coating’s pencil hardness.
The grades are steps in a ranking, not equal measurements. So 4H is simply harder than 2H, not exactly twice as hard. Use the scale to order surfaces from soft to hard, not as a precise number.
What About Uncoated Polycarbonate?
Bare polycarbonate is a soft material and is located at the lower end of the hardness scale. A study published in 2024 reported that the hardness of uncoated polycarbonate film was 2B and was raised to 6H after a specially developed clear coat was applied in the lab. Most hard coats used on phone cases sit lower, at around 2H to 4H. It is important to note that a clear coating increases the hardness of polycarbonate. Tekra Inc. reports that polyester and polycarbonate films are between a B and 4H hardness, depending on the presence of a coating.
This means that an uncoated polycarbonate film is softer than a school pencil and scuffs easily.
The Accuracy of the Test
The pencil test is quite subjective, and the American Coatings Association reports that different laboratories may differ by around one grade. The results of this test are usually expressed as the hardest lead that does not mark or cut the surface.
Tekra adds that when tests are done with a lighter load, the surface appears harder. Therefore, if a brand says 4H and another brand says 4H, the tests may have been conducted differently. In general, when discussing hardness in coatings, numbers should be considered as guidelines and not strict definitions. Keep this in mind whenever you read a clear phone case scratch test claim.
What Does It Mean When a Phone Case Is Tested as 2H vs 4H?
To prevent scratching, it is common to dip or spray polycarbonate with a liquid coating and then expose it to a UV cure.
Let's consider the following 2H vs 4H hardness coating comparison and how each coating performs in real-world situations.
| Feature | 2H vs 4H |
|---|---|
| Overall | A 4H hardness coating is harder than a 2H hardness coating. |
| Pencil rating | A 4H coating will resist scratching by a harder lead than a 2H coating. |
| Light wear | A 4H coating will resist scuffs and scratches better than a 2H coating. |
| Keys and coins | A 4H coating will resist scratches from keys and coins better than a 2H coating. |
| Sand and grit | Both types of coatings will become scratched from these abrasives.. |
| Clarity over time | A 4H coating will usually maintain clarity longer than a 2H coating. |
| Cost to make | A 2H coating costs less to produce than a 4H coating. |
Why Sand Still Scratches a 4H Coating
A 4H hardness coating can be scratched by sand for a couple of reasons. First, sand contains quartz, and quartz has a hardness greater than 4H. Second, the pencil test cannot reveal if a surface will be scratched by abrasives. Quartz grains will scratch a 4H hardness coating.
How a Cross-Linked Surface Resists Scratches
A 4H hardness coating creates a tight cross-linked surface structure, like bricks. A cross-linked surface means that there is very little space for a sharp object to go between the molecules and scratch the surface. To achieve this structure, the coating is cured using ultraviolet (UV) light.
A denser cross-linked network is harder for a sharp point to push into, which is why a higher degree of cure generally means a harder, more scratch-resistant surface. Hardness comes from how well the coating is cured, not from how thick it is. A good hard coat is actually very thin, so the case stays clear.
A Slicker Surface
Many hard coatings also contain slip additives that make the surface less frictional and more slippery; hence, a key slides over the surface rather than sticking to it. Slipping also reduces scratching and allows the case to be more easily wiped clean.
Keeping the Case Clear
A good hard coating keeps a clear case clear and does not haze the back of the case. A good coating is generally very thin.
It’s the scratches, not the coating, that make a clear case look cloudy over time. The real point of having a case is to protect the back of the phone, and a hard coating helps achieve that.
Thinking about appearance? Frosted cases look really good on an iPhone. Check it out yourself. In our article on crystal clear vs frosted cases, we discuss frosted cases vs. clear cases.
Scratch-Proof Clear iPhone Case: You Can Test Case Hardness at Home
A clear phone case scratch test is fairly simple. All you need is a variety of art pencils (i.e., 2B, B, HB, F, H, 2H, 3H, and 4H), sandpaper, and a lab coat. Okay, you don't need a lab coat, but you do need to test the case in a spot that is not visible.
- Use sandpaper to create a sharp, flat edge on the tip of each pencil.
- Find a spot on the case that is not visible and is not near an edge.
- While holding the pencil at a 45-degree angle, push it across the case. Press down with firm, consistent pressure, but not so hard that the lead snaps. Use the same pressure for every pencil.
- See if there is a scratch.
- Repeat with a harder pencil and test again. Continue until a pencil leaves a mark. The last pencil that did not leave a mark is your rough rating.
This is a good indicator of how case hardness compares to the hardness of a pencil, but it does not exactly match hardness ratings.
How to Avoid Scratches on Your Case
As already stated, a 100% scratch-proof clear iPhone case does not exist. So, here are some basic tips to increase the lifespan of your phone case and keep it looking clear for longer.
- Do not carry your phone with your keys and coins.
- When you're done at the beach, brush off the sand from your phone and case, and put them back in your bag.
- When you take your phone out to take a picture, set it face down so the camera isn't in contact with any surfaces.
- You can clean the phone case with mild soap and water and a microfibre cloth.
For information about the two main case materials, read our guide to polycarbonate vs TPU cases. To learn how to remove yellow case discoloration, see how to remove yellow stains from an iPhone case.
Conclusion
This article explains how Scratch-proof clear iPhone cases may not offer 100% protection from scratches, but a good hard coating can significantly improve resistance to everyday scuffs and scratches. In the 2H vs 4H hardness coating tested comparison, both 2H and 4H hard coatings are better than having no coating at all. A 4H coating does a better job of protecting the back of your case from scuffs and haze.
Keep in mind that neither is totally protective against scratches, and the coating can still wear off. Before you buy, check if the manufacturer discloses the hardness of the coatings. Once you receive your case, check out hidden spots to see if the coatings are of good quality. Before you buy, look for a brand that states its hardness rating and test method, and check a hidden spot once your case arrives. If you’d rather avoid haze altogether, explore our super ultra thin cases for a slim, low-profile fit, our carbon fiber cases for a textured opaque finish, or our premium leather cases for a finish that ages with use.
Sources and Further Reading
- ASTM International: D3363 Standard Test Method for Film Hardness by Pencil Test
- American Coatings Association: The Pencil Hardness Conundrum
- Tekra: Tek Tip: Pencil Hardness Test
- Progress in Organic Coatings (2024): Rapid-curing imidazole-based highly transparent protective coating for polycarbonate films
