Thermobond Spa Shell

The basis of a great spa is a great spa shell. Our Thermobond shells use the best of materials and processes to ensure their strength and durability match the best that the world has to offer. The Infinity shell is produced using an 8 step, 4 layer process that is second to none.


Step 1

American made, Aristech acrylic is kept in a climate controlled environment to avoid moisture penetrating the acrylic surface, as is the resin and fibreglass used in the shell construction. When required, the acrylic sheet is hand sanded to assist adhesion to the fibreglass layers.

Step 2

The acrylic sheet is heated in a zone controlled oven before being vacuum formed into the spa mould. The zone controlled heating ensures the thickest possible acrylic shell is formed. This method of zone heating is only used by premium spa manufacturers, as it is the most precise method of acrylic forming available

Step 3

The formed acrylic shell is then sprayed with pure vinyl ester resin. Vinyl ester resin is the industry’s best quality resin. It is also the most expensive resin and therefore, many manufacturers do not use it. This resin gives the acrylic a permanent water seal to eliminate the chances of de-lamintation. It also provides a base for the following layer to adhere to.

Step 4

The shell enters a temperature and humidity controlled curing oven. This process is crucial for resin and fibreglass manufacturing as it ensures that any moisture in the resin or shell evaporates and allows the resin to cure evenly over the shell, creating a permanent water seal.

Step 5

The shell is sprayed with its 2nd & 3rd layer – marine grade, pure polyester resin and glass fibre. This layer bonds with the vinyl ester and acrylic shell to ensure permanent adhesion. It also provides reinforcement to the shell, along with the following layers.

Step 6

The spa re-enters the curing oven for a second pass to cure the polyester resin & glass.

Step 7

The lip of the spa and crucial weak points are strengthened using hand layered fibreglass sheets. At this point, timber blocks are fibre glassed onto the spas shell to provide fixing points for the frame and equipment

Step 8

The shells 4th layer is sprayed using GP resin mixed with stone powder. This layer literally sets like concrete to give unsurpassed shell strength. The torsional rigidity that the stone powder gives the resin, means that our spas do not have to use timber supports under stress areas that many spas rely on