Paintball Splatter
Credit: 27182136@N00/7501782418 on Flickr via CC 2.0

Paintball bruises have a very distinct look which might look like a hickey to some people but if you look closer they are halo shaped. I aim to solve the mystery by demonstrating from my own personal experience when I became a paintball Guinea pig tester in my own bachelor man hunt.

My Paintball Man Hunt

Not too long ago I had my bachelors party which started early Saturday morning. My soon to be brother-in-law whisked me away that fateful morning and had planned the agenda for the rest of the weekend. I was clueless and petrified to what plans he had in store for us. We he had his bachelors party the year before and I knew he was out for revenge. That meant he and my other mates were out to inflict some much needed therapeutic pain relief.  

While all my friends descended on the local paintball club forest location, I learned my soon to be realized fate. They all approached me with a grin on their face and shook my hand. Clearly they knew something I didn’t. My flat mate from university days opened his backpack and hands me an XL adult diaper and tells me this is all the protection that I need. It was well received by my friends!  The club marshal had seemed to have had some experience with the theme of a bachelor man hunt and was not opposed to the idea as long as I wore the face mask.

The rules were explained and I was given 10 seconds head start before the marshal blew his whistle and my mates began to hunt me down. The manhunt ensued and after a few rounds, I was already showing some heavy fire, particularly hits taken on my back and legs. My XL diaper did not provide much padding to my bum and I was able to retrieve a few unbroken paintballs that were lodged in the padding.The Mystery Of Paintball Bruises And Why They Hurt So MuchCredit: Sudocream

How Much Does Paintball Hurt?

Being hit with a paintball feels like a sting but the pain fades quickly within the next 5 seconds.  It is similar to being flicked or a less severe whipping action to the skin.  The degree of pain is dependent on the number of factors which I discuss below. The hits vary from almost no mark to the skin, to deep penetrating bruising to the extreme when the skin tears and bleeds.

Factors Effecting Paintball Pain

Myself and a number of my friends are engineers and know very well the physics and how to inflict the most pain. It was clear during my bachelor man hunt that they enjoyed putting their theories to the test, as I became a living breathing target. 

1. The Impact Surface

The paintball undergoes a collision with the impacting surface and the hardness of the impact surface plays a role on the duration of the collision time. The harder the impacting surface, the shorter the duration time and the greater the force generated. The above physics directly relates to whether it hits your bony hands, elbow or the back of your head versus hitting you in some softer, squidgy areas of the body. The more layers of clothes that you can wear especially if the material is loose and not tight against your body can help increase the collision time and thus reduce the size of the welt.

2. Temperature Of The Day

There is a notable difference from playing in the warm summer than the colder winter. The paintballs are affected by the colder temperatures in two ways. The shell becomes harder and more brittle under colder temperatures, think of it becoming like glass and that the paintball resists collapsing and breaking apart.   The other way the paintball is affected by temperature is that the paint inside becomes more viscose, that means it’s thicker and in a collision the energy spread over a large area but the thick paint centers its self on a smaller localized area. Basically the less splatter in the collision the more it’s going to hurt! That leads me to next important question.

3. Did The Paintball Break Or Bounce During The Collision?

After a couple of rounds of play, you may notice that the paintballs that bounce and ricochet off you hurt the most. In a paintball collision energy is absorbed in breaking the paintball shell and then distributing that momentum energy over a wide splatter surface, which to the person is less painful. When a paintball is fired and does not break on impact and bounces off you, the momentum energy is absorbed by the impact surface which is the size of the paintball. Now that can be really painful.

4. Velocity Of Paintball

This is a pretty obvious point and it boils down to pure change of momentum equations. The paintball mass remains the same but the velocity is higher, results in a higher momentum. So if that paintball hits with a higher velocity it’s going to hurt all that much more. Worldwide the acceptable velocity of paintballs is no more than 300 fps. At this speed bruising is to be expected however at faster speeds, the paintball is likely to do more damage possibly cause bleeding, which is what happened to me. 

5. Flight Time Of The Paintball

Like all projectiles, paintballs that are fired are subject to drag losses from the air resistance through which they fly. The drag losses become greater and greater the more that it travels or the time it flies. When a paintball is fired at close range the least amount of momentum energy has been lost to air resistance resulting in a high impact velocity. My friends took full advantage of this fact and shot me at close quarters.

How Long Do Paintball Bruises Last?

I played paintball a number of times but never under the conditions of my bachelors party. In the past I found that the bruise would last a week to two weeks at most. Wearing nothing but a mask, thin white T-shirt and an XL adult diaper, I realized that the high impact close range shots that caused me to bleed were still visible by the third week.

Paintball bruisesCredit: Sudocream

Why Do Paintballs Give Halo Shaped Welts?

The answer lies in the mechanics of the collision and how the energy of the impact is transferred to the skin. As the paintball impacts the shell begins to deform, the deforming action absorbs the paintballs momentum energy. The paintball continues to deform from the center outwards, until the deformation reaches the edge of the paintball which is structurally the strongest part of the paintball shell. At this point, the paintball shell transfers more energy to the skin. Physically this means that the paintball shell edge at the diameter of the paintball is what causes you to bruise in a halo shape.