As the weather starts to warm up, and the humidity rises, do your casting results change? Ever wonder why this happens? Well investments are made from natural materials, and these materials can react to changes in environment. For example, when temperatures are too hot where investing takes place expansion can be lost and castings will come out fitting tight.
This is why it is so important to store and use your investments in a controlled environment where the temperatures remain between 68°F - 72°F. Keeping a consistent environment in your laboratory is a major key to keeping consistency in your casting results.
If your dental lab is setup in such a way that makes it difficult to control the temperature in your casting area, then utilizing temperature controlled storage equipment could be the answer for you. The best environmental control unit is one that can heat and cool to keep the environment within the cabinet at a constant temperature in summer and in winter. However, these can be quite expensive and often times unnecessary depending on how much the environment in the laboratory is controlled.
In most areas in North America the problems are typically more prone to happen during summer months, when laboratories tend to heat up and get humid. To help with this scenario a more practical device would be one that keeps investments at a temperature around 68°F during the summer months. We've found that a simple solution can be using a small, compact refrigerator and integrating a low cost Ranco thermostat type device.
We strongly discourage the use of devices that can actually lead to heating investments. We've seen companies sell units that direct you to set the temperature anywhere up to 10°F higher than room temperature. These units only heat, they don't cool, which can lead to major problems.
If your powder and liquid are already at temperatures above what is recommended then you will loose expansion, working time and have other problems. Just try a simple test and use some hot water to mix up your investment. You will find that the investment sets up much quicker and it will be difficult to pour into the ring. If you took it one step further and cast a coping with a heated mix, you will find the fit to be tight due to the lost expansion.
So as we move towards the summer months, and things start to heat up, remember that all investments are prone to problems if things get too hot. So make sure you do your best to keep the lab cool or look into some type of device that will allow you to store your investment at constant temperature of around 68°F. This will allow you to achieve the most consistent results throughout the entire year.