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Bathtub Materials Finally Explained

When it comes time to purchase a bathtub, most people are interested in what the bathtub is made from. Acrylic? Cast-Iron? Solid Surface? They want to know that they are getting the best quality material for their money. In this blog, we explain the difference between the materials that are used to build a bathtub. It is also explained what you can use to maintain and clean your tub.


Acrylic is an extruded or continuous cast plastic. Tubs are vacuum-molded (drawn into a mold) from sheets of solid colored acrylic and then reinforced with a fiberglass backing for strength and sound deadening. "Solid" colored means the color goes all the way through the sheet; not just a top layer. This is important because if the tub gets nominally scratched during use, you will not see the scratch as easily as you would when using materials where the top coat has the color and the lower layers do not. Acrylic is popular with manufacturers and consumers because it can be molded into almost any shape and comes in hundreds of colors. It is light, non-porous, easy to

maintain and durable. Additionally, shallow scratches and even dings can be repaired by a professional tub refinisher. Acrylic is also warm to the touch, does not draw heat out of the water like tile or cast iron and is naturally slip-resistant.

To clean acrylic tubs, use a mild, non-abrasive cleaner. If abrasives are used,

they will eventually dull and scratch the luster of the finish.

Tile cleaners and strong household cleaners need not be used.

As always, check the manufacturer’s maintenance instructions.

Cast Iron Cast Iron describes a manufacturing process used for over a century to produce bathtubs. It is a cool metal and with all material seeks to obtain an equal temperature between it and the water; therefore, the water in cast iron tubs cools more rapidly than water in a tub made of acrylic or fiberglass. Also, cast iron bathtubs are heavy and therefore generally limited to sizes up to 72" x 36" and 60" x 42". Attention to this weight factor may be important if you are designing a bathroom that is accessible only up a long flight of stairs. However, cast iron is a tried and true, high quality material that lasts for many years with very little maintenance.

Clean with a mild, non-abrasive cleaner. Do not use scouring pads which can dull the shiny characteristic of cast iron. If you get a hairline crack in the enamel that cannot be felt, water may seep down to the metal and cause a thin line of rust. If this occurs, contact the cast iron manufacture for what is called A/B Solution. This is a two part repair process that can easily be completed by the homeowner. You apply “A” to get rid of the rust and then “B” to seal the crack so that it does not reappear. Stubborn, dark gray marks may be removed by applying a paste of oxalic acid purchased from your grocery or hardware store and letting it set for a few minutes before rinsing. As always, check the manufacturer’s maintenance instructions.

Cast Polymers - Gel-Coated

Cultured marble, onyx, granite and solid colored polymer based materials are used for cast mineral filled polymer fixtures. Although

they are generally referred to as cultured marble or cast polymer. Cast polymer surfaces

are created by pouring a mixture of ground marble or natural stone and polyester resin into a mold. The durability properties of solid colors and granites are the same as standard, culturedmarble. However, these new types of castpolymers are generally equal in expense to solid surface products because of the

additional cost of materials and the need for more careful mold handling in order to create defect-free

solid colors. This polyester gel-coat finish is also not as durable as other surfacing

materials. However, a skilled bathtub refinisher can repair damage to a cast

polymer fixture on the job site.

Clean with a mild, non-abrasive cleaner. Shinier finishes require more gentle maintenance whereas, some matte finishes can take the light use of a scrub pad. As always, check the manufacturer’s maintenance instructions.

Solid Surface Bathtubs - Non-Gel-Coated

A solid surface tub is manufactured much like a cast polymer bath except solid surface products do not use a gel-coat. This means there is not a surface coating that may crack, craze, or yellow. Apart from this distinction the products are cast in the same way. Typically, solid surfaces are harder and more durable than gel-coat finishes.

There is very little maintenance required on solid surface tubs because tub is made of the same material throughout; there are no layers of different material. Any minor scratches can easily be buffed out and other repairs may be made by tub resurfacers. As with other materials, always follow the maintenance requirements as stipulated by the manufacturer.


Copper bathtubs are individually hand-crafted

and therefore best suited for a rustic application, since the tub will not have the

consistency of other types of materials made on an assembly line. These tubs do not offer

any insulation and are therefore noisier and colder than other materials. Most thicknesses of the metal for copper bathtubs are 12 gauge and finishes may be smooth

and or hammered based on preference. These types of bathtubs are more for décor and

not function because of their high maintenance and cost.

Copper tubs are not lacquered and it is nearly

impossible to keep their original, factory finish intact. With this material, it is very

important to follow the manufacturer’s maintenance and cleaning instructions.

Enameled Steel

To fabricate a bathtub in enameled steel, a sheet of steel is pressed into a die so that it forms the desired shape. A powder coat of glass enamel is then applied and fired in an oven. Some enameled steel fixtures also require sections to be welded together. At first glance, enameled steel fixtures look quite similar to cast iron. However, there are dramatic differences. Enameled steel fixtures are more susceptible to damage than some other materials. When a heavy object is dropped on the fixture, the formed steel flexes on impact, whereas the enameled finish does not. This may lead the enamel to chip or cause it to form a smooth, round flake called a “pop-off”. Additionally, the enamel is not completely smooth and forms slight dimples called “orange peeling”. With enameled steel bathtubs, the materials work to equalize in temperature causing the water to become colder as the metal becomes warmer. On the plus side, they are the least expensive fixture you can specify and easy to handle because of their light weight. Maintenance of enameled steel must be done in a very gentle manner. You should never use harsh cleaners nor any scrubbing powders or pads.

Fiberglass and Gel-Coat

Fiberglass bathtubs are manufactured by

spraying a gel-coat onto a mold. Then a multi-layer fiberglass backing is applied

by spray and compacted with a hand roller. As with acrylics, the manufacturing process

allows for numerous shapes, sizes, and color choices. Fiberglass is porous and less

durable than other materials, but like acrylic does not cool the bath water as quickly

as cast iron, metal, or enameled steel. Additionally, the color is only on the

top layer with white fiberglass underneath, so scratches are more noticeable than

with other products and repairs are difficult. As this product is cleaned, it may become dull

and show surface scratches and swirl marks.

Clean with mild soap and water. If abrasives are used, they will damage the luster of the finish. Use a sponge or other non-abrasive applicator. Never use a scouring pad or steel wool. Some professionals suggest applying a car wax to the fiberglass after each cleaning to make it less porous and easier to clean. It is important to abide by the manufacturer’s maintenance instructions when it comes to taking care of fiberglass tubs.


Stainless steel tubs follow the same manufacturing process as enameled steel fixtures where a steel sheet is pressed into a die; however, no surface coat of enamel is applied. Stainless steel quality is judged by the steel gauge, the nickel content of the fixture and the finishing process. The higher the gauge number, the thinner the steel. 16 gauge steel is considered the best product for luxury projects with 18 gauge the next best option. 20 gauge steel is also available and may be acceptable. However, 22 gauge steel should only be used in low budget projects. Nickel in the steel increases the corrosion

and stain-resistant qualities of the fixture, so it is important to offer product with a

high enough nickel content. European products typically have higher

nickel content than those manufactured elsewhere, such as Asia. Additionally, you want a product with a multi-step finishing process which refines the finish. Keep in mind that a brushed finish is easier to care for and maintain its initial appearance than a mirrored finish.

Since there are numerous types of metals and finishes, it is imperative to check manufacturer’s recommendations.


In some areas of the country, tile is a very popular bathroom surface material. Customers may want their tile contractor to design and make the tub. Many sizes and shapes are possible because of its customization. Be sure the grout and cement in these installations are kept to a minimum

for easier maintenance. These tubs may have the faucet deck- or wall-mounted. Maintenance of tile bathtubs is much like that for tile floors by using mild cleansers.

Sometimes after installation and the first initial uses, your client may notice little rust

sliver stains on the tile.This is due to many tile installers using steel wool to clean the haze left on the tile during the grouting process. The steel wool slivers left behind on the tile get wet and rust. The rust is easily removed with a calcium/lime/rust remover; just follow the manufacture of the rust remover’s instructions. It is also important to seal the grout before the first use and approximately each year there after with a grout sealer.


Several manufacturers offer wood bathtubs. Wood fixtures are generally constructed from solid strips of oak or teak. Teak wood is considered more desirable than any other species because of its oily composition, which minimizes its expansion and contraction properties. Once constructed, the fixtures are finished with a polyethylene coating to protect and enhance the beauty of the wood. To add to the structural integrity of the fixture, as well as to aid in heat retention, the outsides of wood bathtubs are generally sheathed in fiberglass.

Wood fixtures should not be exposed to constant, direct sunlight and need to be wiped down after each use to avoid the development

of a permanent, unattractive water line. If damaged, the polyethylene finish can be repaired. Only use mild cleansers and follow the manufacturer’s cleaning recommendations.

If you have any questions about the way bathtubs are made, please reach out to Flow. To get your dream bathtub, visit us at 127 S. Easton Road Glenside, PA 19038 or call at (215)-454-2258.

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