Rather than directly adding gas to molten metal, it is possible to add a powdered material or compound which is stable at room temperature, but which will decompose at a higher temperature to give off a gas. By using a solid foaming agent it is possible to disperse gas more uniformly throughout the melt. Titanium hydride, TiH₂, is well suited to this process as it is stable at room temperature, but readily decomposes at temperatures similar to the melting point of aluminium to give off large volumes of hydrogen gas.

In order to prevent the bubbles of gas from coalescing, floating or escaping from the melt, it is necessary to increase the melt viscosity. This can be achieved by mixing powders or fibres into the melt. In an alternative approach, developed by the Shinko Wire Company, approximately 1.5wt.% of Ca or Mg is stirred into an aluminium melt at 680ºC, and air is bubbled through the melt. By promoting oxidation of the melt, this forms a dispersion of fine oxide particles throughout the molten metal, raising its viscosity.

In the Shinko Wire Company process, 1.6% wt.% of TiH₂ is added to this melt and stirred thoroughly, followed by a 15 minute curing time where the foam is held at 680ºC and the hydride decomposes according to the reaction:

This forms pores within the viscous melt, producing foams with porosities between 84 and 95%, and cell sizes of approximately 5mm. Batches are routinely made weighing up to 160kg.

The foams have a significantly more homogenous microstructure that those produced by direct addition of gas, and do not require the addition of silicon carbide particles. The process is easily scaled up, but remains expensive and relatively hazardous, due to the use of calcium and the need to handle escaped hydrogen gas.

Exploiting the fact that foaming takes place over a reasonably long time, foam injection moulding techniques have been developed using chemical foaming agents. In a typical process the precursor is heated to the decomposition temperature of the foaming agent, and immediately fed in to a standard casting mould. Foaming starts before the foam enters the mould, and continues inside the mould to fill the volume, producing a shaped foamed body with a solid outer skin. The form and homogeneity of the cell structure is closely dependent on details of the process parameters. In a further extension of this technique, injection moulded foam parts have been used in place of the sand cores sometimes included to create hollow regions in conventional solid injection castings. The foams survive the addition of solid metal during the second casting stage, and can be left inside the final structures as low-density material reinforcement.