What are "wet process" and "dry process" aluminum hydroxide, and how do they differ?

Are you confused by terms like "wet" and "dry" aluminum hydroxide? This confusion can lead to buying the wrong product or paying for unnecessary processing.

"Wet process" aluminum hydroxide refers to the product as a wet cake or slurry, straight from production. "Dry process" aluminum hydroxide is the same material that has been dried into the fine white powder most customers are familiar with. The main difference is physical form and water content, not chemical quality.

In my years managing production at our plant, I’ve seen many buyers assume that "wet" means lower grade. This isn’t true at all. The choice between wet and dry product is purely about logistics, storage, and the customer’s specific application. In fact, some of our local customers prefer the wet cake because it can be pumped directly into their own production lines, saving them a step. Understanding this difference is the first step, but it often leads to more questions about the product itself. Let’s dig into some of the most common ones I hear from buyers.

What is dried aluminium hydroxide gel?

Are you working in pharmaceuticals? Sourcing the right grade of "aluminum hydroxide" can be a major challenge for your formulations if you get the wrong type.

Dried aluminum hydroxide gel is a specific, amorphous (non-crystalline) form of aluminum hydroxide used mainly as a pharmaceutical antacid. It is chemically different from the crystalline industrial-grade aluminum hydroxide used as a flame retardant or filler.

At our factory, we specialize in producing industrial-grade aluminum trihydrate¹, or ATH, which has a very ordered crystalline structure² called Gibbsite³. This structure is key for its performance as a flame retardant⁴. A few years ago, a potential buyer from a pharmaceutical company asked for a quote. He sent a spec sheet for "dried aluminum hydroxide gel⁵." I had to explain that while they share the same basic name, the two products are completely different. Think of it like carbon: a diamond and a piece of charcoal are both carbon, but their structure and use are worlds apart. The gel is made through a chemical precipitation process that results in an amorphous structure with a high surface area, making it effective for neutralizing stomach acid. Our product is made through the Bayer process⁶, designed for large-scale industrial use.

Here is a simple breakdown:

Understanding this distinction is crucial. Using industrial ATH in a pharmaceutical product would not work, and using the expensive gel in an industrial application would be a waste of money.

Is aluminum trihydrate the same as aluminum hydroxide?

Are you seeing different names for what looks like the same white powder? This can cause confusion in technical documents and purchase orders, leading to costly mistakes.

Yes, aluminum trihydrate (often shortened to ATH) is the exact same chemical compound as aluminum hydroxide. The chemical formula is Al(OH)₃. The different names are simply used in different contexts and industries.

This is one of the most common points of confusion I clarify for new customers. In chemistry, the proper name is aluminum hydroxide. However, in the industries we serve, especially plastics, rubber, and solid surfaces, everyone calls it Aluminum Trihydrate or ATH. Why? The name "trihydrate" helps to emphasize the "three water molecules" part of its structure (you can also write the formula as Al₂O₃·3H₂O). This is very important for its main application as a flame retardant. When ATH is heated to over 200°C, it breaks down and releases these water molecules as steam. This process absorbs a lot of heat and dilutes flammable gases, which is what stops or slows the fire. So, the industry calls it ATH to constantly remind users of this key functional property. When I first moved from production management to sales, I made sure my team understood this. A customer asking for ATH is looking for the same product as one asking for aluminum hydroxide; they just work in an industry that uses the common name.

Here’s a quick guide to who uses which name:

What is another name for aluminum hydroxide?

Do you find it hard to search for a material when it has multiple names? Using the right keyword can be the difference between finding the right supplier and getting lost.

Besides aluminum hydroxide and aluminum trihydrate (ATH), it is also called hydrated alumina. In its natural mineral form, it’s known as Gibbsite, Bayerite, or Nordstrandite. Gibbsite is the most common and industrially important crystal form.

When we talk about our product, we are almost always talking about the Gibbsite crystal structure. The Bayer process, which is the standard industrial method for producing aluminum hydroxide from bauxite ore, naturally produces Gibbsite. It’s the most stable form. The other names, like Bayerite and Nordstrandite, are what chemists call "polymorphs⁷"—they have the same Al(OH)₃ chemical formula but the atoms are arranged in a slightly different crystal structure. These other forms have different properties and are much less common in industrial applications. Sometimes, an experienced buyer with a very specific technical need, for example in catalysts, will specify the exact mineral form they require. When a customer’s inquiry specifically mentions "Gibbsite," it tells me they are a knowledgeable professional who understands the material science behind their application. It’s a clear signal that they value quality and consistency in the crystal structure, which is something we pride ourselves on at our factory. Knowing these names helps you speak the same language as producers and technical experts.

Is aluminum hydroxide the same as aluminum?

Are you worried about confusing basic materials? Mixing up a compound like aluminum hydroxide with the pure metal aluminum could lead to serious application and safety issues.

No, they are completely different substances. Aluminum (Al) is a pure metallic element that is shiny and conducts electricity. Aluminum hydroxide (Al(OH)₃) is a chemical compound—a white powder that does not conduct electricity and is not a metal.

This question might seem basic, but it’s a critical safety and application point. You cannot substitute one for the other. Think of it this way: pure iron is a strong metal used to make steel. Rust, which is iron oxide, is a flaky powder that is a product of iron’s corrosion. They both contain iron, but you would never build a bridge with rust. It’s the same principle here. Aluminum is a lightweight metal we see every day in drink cans, window frames, and airplane parts. It’s produced by smelting a different aluminum compound, alumina (Al₂O₃). Our product, aluminum hydroxide, is actually an intermediate step in the process of making aluminum metal. We take bauxite ore, use the Bayer process to create pure aluminum hydroxide, and most of this worldwide is then heated (calcined) to create alumina for metal production. We simply stop the process and refine the aluminum hydroxide for its own unique applications.

Here is a clear comparison:

Conclusion

Understanding these key terms is simple. "Wet" vs. "dry" is about physical form, not quality, and knowing the different names like ATH and Gibbsite helps you communicate clearly.