Resin and Humidity Tips by The Mould Story

Resin is a chemical that goes through a chemical reaction. Any excess water can interfere with this reaction, or affect the transparency of the resin. 

This happens because of Amine’s in the resin which are hygroscopic. Hygroscopic means it absorbs moisture from the air. The amine’s absorb moisture, and the surface of your resin will appear cloudy after or during the curing of the epoxy.

It will look like a sticky, greasy, oily or waxy surface on the top of your resin. 

What is humidity? 

Humidity is a percentage that expresses the amount of water vapour in the air. 100% humidity means the air can no longer hold any water, and therefore we have RAIN!

In our daily lives, our air holds water too. In Mumbai during the least humid month, humidity is only 62%. In the monsoons however, humidity can be up to 95%!

What is the humidity in my home?

Humidity in the home can be more or less the same as outside, unless you have all the windows closed and are running appliances and generating dry air that reduces humidity.

What is the correct humidity level for resin casting?

Resin can be cast in humidity between 50-80%. But the closer you are to 50% the less likely to have Amine Blushing and less chances of your product being affected by moisture. 

How do I check humidity?

1. You can type into google the humidity level and weather for your area. This will give you a general idea of the conditions for that day.

2. Get an inexpensive Humidity meter from Amazon. It surprises me that there are resin artists who still do not have this 300 rupee lifesaver!

Amine Blush - The enemy!

What are the effects of Amine Blush?

Amine blush is the enemy because it can cause the following problems:

1. Cloudy appearance on the surface of resin making it look ugly
2. The amine blush layer can act as a bond breaker between layer pours
3. Faster yellowing of the resin cast
4. Curing state is affected not achieving final hardness

Remember that amine blush may not occur all throughout the cast but in certain areas only. This is because of uneven ventilation etc. 

What do I do if I have Amine Blusing?

Amine Blushing is water soluble, so you can’t remove it with solvents. However you can use soap, and a scrubbing brush to scrub it off. This will obviously make your casting matte and will require sanding, which you can only do after the surface is completely dry. Following which you will have to do a topcoat.

How can I avoid this terrible Amine Blush!

Did you buy a humidity meter as yet? If not, how will you know the level of humidity in the air, and whether your casting is at risk or not? Please go buy a humidity meter from amazon NOW!

Once you know the humidity in the air, you can take the steps to control it.

Steps to control humidity

1. Run a dehumidifier. This machine sucks out the water from the air and you can save the planet by using that water to flush your toilet or water your plants. A demudifier cannot remove water from the whole house, so make sure you are using it in as small a room as is comfortable without open windows and don’t keep opening doors. 

2. Run an air conditioner at dry mode at a temperature of 23 degrees. Colder air holds less humidity, and an air conditioner on dry mode will help reduce moisture in the air. 

3. Put bowls of salt around the room. Big bowls of rock salt. This is a natural dehumdifier and rock salt is hygroscopic and will absorb the moisture from the air.

4. Use moisture absorbing products like Silica Gel or Absorbia and put them around the room.

HACK! The smaller the area the more effective moisture absorbing products are right. Get a big plastic crate to cover your resin casting and put the moisture absorbers in there. Even if you don’t have an AC or a dehumidifier, a bowl of rock salt or absorbia or silica gel packets will help you keep the moisture conditions right for casting!

Happy Casting and Monsoons!