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Does Styrofoam Float? (Quick Answers)

Styrofoam is a material that goes by many other names. That is also without stating the fact that the name styrofoam is also a trademark for the chemical compound that is called polystyrene.

Now, polystyrene is often mistaken for the brand name Styrofoam. Styrofoam can be found in many different household lightweight products like containers, egg cartons, packaging of fragile products, coffee cups, and more.

However, polystyrene products are usually used for building insulation. These are the uses that we can see on a large scale unlike the small products like before. No wonder Styrofoam has become a brand name that almost all walks of people know about. 

One of the most common materials made from the styrofoam brand name is the plastic foam which is made from the polystyrene material. This plastic foam is widely used in various things for our consumption or usage.

You might be wondering what polystyrene is and what it has to do with styrofoam. Polystyrene is a petroleum-based plastic made from styrene monomers. This material is so lightweight that it almost has 95 percent of the air in it and thus as a result it is indeed good for insulation.

But you are here to know about the product at hand, you want to know more about the plastic foam, the brand name “Styrofoam”. Today we will be discussing these products’ properties, behavior, how it functions, and many more different aspects.

We will answer the burning question, “Does Styrofoam float?”. So, do not dilly dally and keep reading below to know more about this branded product and if it floats or not. 

Does styrofoam float?

Styrofoam floats on water. We have seen this phenomenon multiple times in the wild, the floating of things on the water is not uncommon. Floating is the balance between the weight of an object and the buoyant force. The density of water is greater than that of the Styrofoam. 

Styrofoam is made from styrene. This is a particular type of product that is petroleum-based material. The process involves polymerization.

The styrene material gets refined into polystyrene and after that, the product gets a hydrofluorocarbon agent. After mixing that agent, the materials are extruded and finally allowed to expand under pressure. The final result is the foam board.

In water: 

Styrofoam will float on water as the product has little to zero density. Because of that when that density is compared with that of water, the difference is vast. As a result, the buoyant force keeps the Styrofoam afloat.   

In rubbing alcohol: 

There are two types of rubbing alcohol, there is isopropyl-based rubbing alcohol and there is ethanol-based rubbing alcohol. Isopropyl-based rubbing alcohol is the most popular one.
If we happen to have denatured ethanol-based rubbing alcohol then it will not dissolve the styrofoam. If we have isopropyl-based alcohol, the styrofoam will dissolve before it has the chance to stay afloat.
However, if we have a lower concentration of isopropyl rubbing alcohol it will keep the styrofoam afloat and not damage it. 

Does styrofoam ever sink?

Styrofoam is a literal product of plastic. That has water-resistant properties but is technically not waterproof all the way. The product is non-hygroscopic and thus it will not take water from around its surroundings.

However, if water were to come in direct contact with the styrofoam then that would be a problem. The styrofoam will absorb the water. Moreover, according to Eriksen, the density of polystyrene (material from which styrofoam is made) is around 1.05 – 1.07 g/ml.

This means polystyrene should sink to the bottom of the ocean. This is because ocean water has less density than that. But that does not happen. Why is that?

That is because the styrofoam has so much volume when it expands that there is air injected into it. Therefore, that fact alone makes it less dense and allows the styrofoam to never sink

Does styrofoam absorb water?

Styrofoam is an iteration of plastic. Some people call it plastic foam. There is an abundant amount of polymer in it.

The product itself is not fully waterproof. Styrofoam is rather non-hygroscopic and that means it will not absorb moisture from the air in any way or process. However, they will absorb water when they come in direct contact with water or moisture

Therefore, to clarify the question, styrofoam will absorb water when it comes in contact with them.  

Why does styrofoam float? 

The reason for the styrofoam float can be a lot of things. Let us briefly go over the details as to why styrofoam floats. 

Not Tight: 

Styrofoam has a very low consistency when it comes to its material. This allows it to stay floating very well because of that free space inside of its body.   

Buoyant Force: 

Things will stay afloat because of many things and one of them is because of buoyant force. It depends on the object if it’s dense or not. In this case, how compact the particles are.  


If the density of the product is less than the density of water, then that particular object will float. This is also true for styrofoam. We know that styrofoam’s density is lower than that of the water, thus it allows it to float on water.   


Styrofoam is generally a foam that is made of Polystyrene. The density of the polymer is almost the same as water. However, due to the large volume of styrofoam, the material contains a lot of air. 

We all know air is far less dense than water. As a result, styrofoam can float it. 

How much weight can styrofoam float? 

Styrofoam can weigh almost nothing. The product itself has less density than water. The material it is made from expands in volume so much that it has a lot of air inside it. 

All of these facts allow it to float on water with ease. In case you are wondering how much weight can they maintain while staying afloat? Then we can answer that for you.

We all know water weighs around 62.4 lb/cubic foot. One cubic foot of foam can at least support a maximum weight of 62 lbs. This is obvious considering the fact that no water will enter the foam. 

How much styrofoam to float 100 pounds? 

We already know that styrofoam can reach the maximum of 62 lbs weight and support that with ease while it stays afloat. However, if we were to increase the amount of weight it can support then we would also need to increase the amount of styrofoam as well. 

To avoid getting the object on the styrofoam that will weigh around 100 pounds. We would need 2767.99047 inches or 105 pounds of styrofoam

How to make styrofoam fishing floats? 

There are many uses for the product styrofoam. They are not just used for packaging fragile objects to ship them safely. They can be seen being used for several other purposes. 

Furthermore, we can even use them as fishing bobbers when we want to. Here is how you can do it yourself in your home easily. 

Measure the styrofoam: 

Take the styrofoam piece, and measure the amount of the desired size you need. After taking the proper measurements, place the styrofoam on a worktable otherwise you might damage the material underneath while cutting it.   

Cut the styrofoam as measured: 

Take a box cutter and simply cut the styrofoam as you measured before. Once we cut through the styrofoam to the desired shapes we have to proceed with making it usable with wires. 

Make them usable with the wire: 

To make the pieces of styrofoam usable for fishing, we need to make them usable with the wire. We can do that easily with a heated nail. We can take a candle and heat a nail for 20-30 seconds and just push it through the styrofoam right down the middle. 

Loop the wire around the styrofoam: 

Once we have the desired holes on the styrofoam pieces, we can loop the wire around them and tighten them as we wish before using them in the wild. In this way, we can make right in our homes, affordable and easy-to-use fishing floats with styrofoam. 

Final Thoughts 

Styrofoam is a material that is notorious for its many uses. They look like normal foam that will melt or evaporate. However, these will not melt or evaporate, as they are plastic foam. They can stay afloat on the water as well due to their density being as low as water.