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Bathtubs come in a variety of materials, but not all are created equal. What's the best material for heat retention? What's the most durable? What else should you consider when shopping for a new tub?
The most common bathtub materials typically found in home construction are fiberglass, acrylic, or ceramic. These are cheaper, which means they can be great options if you're on a budget—but they fail to hold much heat. Some are also porous, which means moisture and body oils can infiltrate the material, making these tubs a little more difficult to clean.
On the higher or custom end, you'll find tub materials that hold heat much better. These include copper, cast iron, marble, stone resin, and porcelain. These are non-porous for the most part, meaning they don't absorb moisture or grime. They do require gentler cleaning, however, to avoid damaging these more premium materials.
Let's take a look at 9 of the most popular bathtub materials to help guide your research.
Fiberglass is one of the most common materials used for bathtubs due to its affordability and ease in manufacturing. It's basically plastic layered into a bathtub mold, which is then coated with gelcoat resin. These tubs are light and easy to move into a house, in addition to offering ease of repair.
However, being brittle and porous, fiberglass disadvantages can include a deterioration of color and finish over time. This means that in a few years, your tub might not look as good as it once did. And the gelcoat coating can be susceptible to staining and yellowing. Fiberglass is also more easily damaged than other tubs, so if you drop something on the surface of your bathtub, it could chip or crack.
Acrylic is made from resins, fillers, stabilizers, and petrochemicals. It's molded into a tub shape, after which it's fortified with fiberglass. Acrylic tubs, while still classed as a budget option, are non-porous and will retain heat fairly well.
Its disadvantages include a tendency to bend and flex, which gives it a less sturdy feeling when you step into the tub. It's not going to give you the feel of a high-end or luxury tub. It's also a little more expensive than fiberglass.
Ceramic bathtubs can either be made of smooth ceramic inside and out, or covered with ceramic tile on the outer surface. Ceramic tile is very customizable—virtually any shape, size, or design can be tailored to fit your bathroom—and it’s a strong and durable material.
Ceramic tubs are reasonably cost-effective, but they are also more susceptible to chips or cracks that can grow and harbor bacteria. And while ceramic tiles can definitely look very elegant, it can also be difficult to keep the grout clean.
Porcelain bathtubs are actually cast iron or steel coated with porcelain. They hold a sheen longer and tend to have a somewhat antique look (which might be a plus or minus, depending on your design preference). They're also easy to clean with baking soda and water or with mild soap.
The trouble with porcelain is that it chips easily, and doesn't retain heat very well. This might be a dealbreaker if you like to take those extra long soaks. What's more, this is one of the slipperiest bathtub materials—you could slip and fall in a porcelain tub unless you put down non-slip stickers or a mat.
5. Stone Resin
Resins can come from either plants or chemical compounds. Either way, they're reduced to powder, mixed with water, and baked into a certain form, much like firing a clay item in a kiln. Resin items last just about a lifetime, are non-porous, and resist color fading, as well as the usual bathtub punishments.
Stone resin holds heat quite well, is easy to clean with mild soap and water, and is completely recyclable when you want to renovate the bathroom. The only real con to stone resin tubs is the price!
6. Cast Iron
The first picture that comes to mind at the mention of cast iron tubs is the venerable claw-foot tub. Strong and durable, cast iron tubs have the highest heat retention. They're also difficult to chip or scratch. Cleaning them is, again, a simple matter of mild soap and water.
The major disadvantage to cast iron tubs is the need to reinforce the floor beneath them. Cast iron is incredibly heavy, so it's usually not an option for a lot of bathrooms (especially those on upper floors) without strengthening the floor beneath.
Copper has a gorgeous sheen that no other material can provide—just think of shining copper pans hanging overhead in a kitchen. As it's a metal, copper retains heat quite well. It's also easy to clean with mild soap and warm water and resists chipping and scratching.
The biggest con of a copper bathtub is that it's about as heavy as cast iron. The floor beneath it will require reinforcing. Copper tubs can also be a little more difficult to find, so you can expect to pay a premium for that.
Much like hardwood floors, shiplap, and other wood products, wooden tubs are a thing of beauty. They're most commonly associated with the Japanese ofuro style. Elegant and aesthetically pleasing, these tubs give a real sense of earthy warmth—and not just because they retain heat.
However, wooden tubs do require re-sealing every so often to stave off wood rot. And just like with wooden hot tubs, poor maintenance can contribute to the rotting of these tubs. They, too, may require reinforcement of the floors due to their weight. Lastly, wooden tubs are not going to be the cheapest.
9. Cultured Marble
With this material, you'll feel like you're in the baths of the ancient Roman Empire. You have quite a choice of color, shape, and size here too. Natural stone retains heat, so your bath will be warm as well as elegant. Cleaning should be done while the tub is still wet, and know that leaving out this step could invite discoloration and mildew. Thankfully, a little vinegar and warm water are all that's necessary to clean a marble bathtub.
The main disadvantage of cultured marble bathtubs is the weight. And along with this kind of luxury comes a more expensive bathing experience. Marble can also be scratched, though thankfully it's fairly easy to repair.
How do I tell what my existing bathtub is made of?
Unless your house is custom designed and built, then general contractors often use big box stores to supply the houses they're building. Most of these stores stock acrylic and fiberglass tubs to keep costs down. If your tub looks like plastic, and bends easily, then it's most likely one of these materials.
Another simple way to tell is to place a magnet on the tub. If it sticks, then there's steel or cast iron covered in enamel. If not, you likely have an acrylic or fiberglass tub. If it's any of the fancier materials such as ceramic, wood or copper, you'll know from the unusual look as these are quite distinctive.
What bathtub material holds heat best?
Cast iron, stone resin, or copper bathtubs have the best heat retention. This makes them great for colder climates or anyone who enjoys a nice long soak in the tub without worrying about the water getting cold.
Cast iron in particular loses its heat slowly and evenly; it doesn't get too hot the way metal can, then cool quickly like plastic (acrylic or fiberglass).
What bathtub material is easiest to clean?
Porcelain, stone resin, cast iron, and copper are among the easiest bathtub materials to clean. What matters is the outer surface texture, not so much the material itself.
For example, cast iron is generally easy to clean thanks to its shiny enamel coating, while stone resin tends to be easy to clean because it's just plastic, even though it's made to look like natural stone.
Can bathtubs rust?
Depending on the material, yes, some bathtubs can rust. Iron and steel for example will corrode over time if exposed to water while uncoated. However, with an enamel or porcelain coating on your tubs that allows you to enjoy its benefits without worrying about corrosion and rust which degrade the tub and could cause leaks. That's why it's important to repair any chips or scratches as soon as possible.
Even if the body of your tub isn't made from metal, you could still get rust around metal components like the faucet and drain especially if they're older. If this happens, your best bet might be to replace them with newer equivalents.
Do acrylic tubs crack?
In time, most material will deteriorate to some extent, and acrylic is no exception—it can also crack due to harsh treatment or just age. If this happens, you can often fill a minor crack with a silicone sealer. Let it dry, and you'll be good to go.
If it's an old tub that's begun to crack due to age, then it may be time for an upgrade. The good thing about replacing your bathtub is that there are more materials available than ever, so you don't even have to go for another acrylic tub—you can choose the one that best fits your lifestyle and budget.
Can acrylic tubs turn yellow?
No, the color of acrylic tubs is set when the layers of plastic are molded into a tub so it's unlikely that an acrylic tub will turn yellow. The material is non-porous, so discoloration from contaminants also isn't a worry provided you keep it clean. If your acrylic tub is dirty, you can clean it using white vinegar and warm water.