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How Are Sponges Made?

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This question originally appeared on Quora.
Answer by Aaron Memon, Student, Amateur Photographer

So let's start by identifying the four main types of sponges: cellulose, melamine, animal, and loofa.


Sheets of cellulose fiber are soaked in chemicals to render them pliable and soft. The sheets, hemp fiber and sodium sulphate crystals, are then placed in large rotating containers to blend the ingredients. When the mixture is thoroughly mixed in the rotating vats, it is poured into a mold and heated. The heat melts the sodium sulphate crystals, which flow to the bottom, where the liquid is removed. The pores or gaps left from the melted crystals form the familiar structure we see in finished sponges. The size of the crystals determines the size of the pores and the eventual use of the sponge. Large pores are used to make big sponges for washing cars, walls, and floors, while finely perforated material can be sold for beauty and art applications. The material, a hard block, next must be softened and cleaned. The blocks are first soaked in bleach to remove impurities and to ensure consistent coloring. Next, repeated soaking and rinsing in clean water completes the process, leaving the sponge material pliable and ready for drying and cutting.


elamine =
agic Eraser type sponge! This is actually considered a
, but same difference. Here's an excerpt from an article that I read:

To all outward appearances, however, melamine foam erasers look and feel just like any other sponge. To view the crucial properties of melamine foam, you need to go down to the microscopic level. This is because when melamine resin cures into foam, its microstructure becomes very hard -- almost as hard as glass -- causing it to perform on stains a lot like super-fine sandpaper. You may be asking yourself, if this foam is almost as hard as glass, then how can it be like a sponge? Because it's a special type of open-cell foam.

Closed-cell foam is easier to visualize, so let's start there. Types of closed-cell foam are usually the more rigid because they retain most of their air pockets intact, like a bunch of balls all crammed together. For open-cell foam (typically the more flexible) imagine that those balls have burst, but that some sections of their casings still remain. You can picture a squishy sea sponge as an example. In airy melamine foam, only a very limited amount of casing stays in place, and the strands that do are located where the edges of several air pockets overlapped. The foam is flexible because each tiny strand is so slender and small that bending the entire eraser is easy.

The cavity-ridden open microstructure of melamine foam is where the second major boost to its stain-removing capabilities comes in. Apart from being able to scrape at stains with extremely hard microscopic filaments, with a few quick runs of the eraser, the stain has already started to come away. That's aided by the fact that the dirt is pulled into the open spaces between the spindly skeletal strands and bound there. These two factors combined make this next-generation eraser seem almost magical.

Here's the article I got this information from: HowStuffWorks "Melamine Foam".


Not the animal shaped kitchen sponges! This category is broken down into three
subcategories: glass sponges, demosponges, and calcareous sponges.

Glass Sponges:

- Have fragile, glass like spicules (tiny spike like structures)


- Make up 90% of the living sponge population

- vibrantly colored

- largest of all three types

Calcareous Sponges

Have spicules made up of calcium carbonate

- smaller than the other types

How's it formed?

Most sponges are just like sacs with perforated with pores. The cells in a sponge don't form individual organs. A sponge's structure consists of spicules.

Read more here: Life of a Sponge

Loofah Sponges

Loofah sponges are harvested from long, thin gourds from the family
Different varieties of loofah gourds produce sponges with different densities and colors. They are generally grown in a hot climate and watered frequently in their earlier stages of growth. Loofah gourds are ready to be harvested after their green color turns into a
brown or beige
. The blossom on top of the gourd is then removed and the
"vascular bundle"
is pulled like a zipper to remove the skin. The loofah is then given a water bath, and if discolored, a diluted bleach-water bath. The loofah is then hung outside to dry (then sun and wind will also lighten the color tone of the loofah).
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