Clean Rooftop Tent Mildew (or Mold) with a Much Better Alternative to Vinegar

Most mold and mildew killers don’t stop them from constantly coming back. The problem is that they grow roots into porous surfaces. But the killers (bleach and vinegar, for example) only get to the surface. You are going to need something more substantial to keep the mold and mildew from coming back.

One effective commercial product points the way toward a truly effective do-it-yourself method. The product is called Concrobium Mold Control Mold Inhibitor. It’s active ingredient is sodium carbonate, or wash soda. But actually there are three ingredients working together to kill mold and mildew and keep them from coming back. Looking at the patent for the product, we can see there are three main ingredients: sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3) and trisodium phosphate (Na3PO4). After doing some research on the ingredients I stumbled onto a blog discussing this issue and providing a DIY solution. This will work on rooftop tents.

Remove and Prevent Mildew for Pennies – The $tingy Sailor

DIY Concrobium knock-off formula:

Borax mildew treatment:

Apply and let it sit to soak in. Then scrub it. Rinse and add another application that will remain. This last application will leave a thin film that kills any new mold or mildew.

The author claims the second formula with the borax is even better than the first.

Note: I added the Amazon.Com links to help you understand the chemicals better. You can probably find all of them locally.

He has tested his formulas while I have not tested my formula below.

My formula (calculations at bottom of page):

  • 1 quart of hot water
  • .2 tsp of baking soda (a little less than 1/4 teaspoon)
  • .75 tsp of wash soda
  • 2.4 tsp of trisodium phosphate

There are a lot of methods that kill mold but they either don’t work very well or the mold/mildew keeps coming back. For example, steam cleaning can work for a tent but it’s a lot of work. The heat kills the mold/mildew. However, if you have a large problem then it’s too difficult.

Below is some background information about the problem of killing mold with bleach.

I use some bleach at home for spot mold in places but it keeps coming back. The reason is that the mold’s hypae (root structure) can grow into porous material. The bleach only kills on the surface and can’t get into the root structure.

In order to get at the root structure you need a surfactant. Surfactants lower the surface tension of water. Surfactants are also called emulsifiers. Examples would be soap, detergent and borax. They allow the cleaner to get down into the porous surface. Or more likely just use the surfactants to dislodge more of the mold and rinse it off.

Here is one guy’s tent cleaning adventure: Winter Tent Prep – Natural Mould Treatment | Shoestring Sustainability.

For tents, using bleach is probably not a great idea because it might fade the material or damage it. You would have to test it on a small area first.

Formula calculations

My chemistry is a little rusty but luckily this exercise is mostly about keeping track of units. And you need to know what a “mole” is.

Looking at the patent for the product, we can see there are three main ingredients: sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3) and trisodium phosphate (Na3PO4) with molar ratio of 1:4:5.

Quick chemistry lesson. The mole (molar) is a way to convert count into weight. Think of a mole as a container which contains the same number of molecules – 6.022×10^23. Bigger molecules will weigh more and have a bigger container in order to have the same number of molecules. When we work with chemical formulas we are working with containers (count.) One container of this goes with 4 containers of that and 5 containers of something else. Instead of container we use the name mole. Now we need a way to convert moles (containers) to grams of weight.

The periodic table gives us the molar weight (container weight) of each element. We just need to add them up to get the molar mass of a molecule. Or you can just google it:

Sodium Bicarbonate: 84.007g/mole
Sodium Carbonate: 105.9888 g/mole
Trisodium Phosphate: 163.94 g/mole

We want a molar ratio of 1:4:5. Here’s how:

moles x g/mole = g (an exercise in “unit” tracking)

(1 mole)x(84.007g/mole) to 4×105.9888 to 5×163.94 in grams

Divide everything by 84.007 to get a weight ratio:

1 to 5.0467 to 9.6980 => these are weight ratios with no units. Roughly it’s 1 to 5 to 10.

My formula by weight ratios:

1 part baking soda + 5 parts wash soda + 10 parts trisodium phosphate

We know from the safety data sheet the following:

That means the wash soda can vary from about .5% to 1%, so the trisodium phosphate varies from 1% to 2% based on the ratios of weight above. Trisodium phosphate is double the wash soda by weight. If the wash soda is 1% by weight then the trisodium phosphate is 2%. And baking soda would be .2%.

Let’s assume the wash soda is 1%.

My formula by percent weight:

1quart water + .2% baking soda + 1% wash soda + 2% trisodium phosphate

A quart of water weighs 946.35 grams. 1% is 9.46 grams for wash soda, 18.92 grams for trisodim phospate and 1.89 grams for baking soda. Note that this is an approximation because the water weight does not include everything but it is close enough.

My formula by weight:

1quart water + 1.89g baking soda + 9.46g wash soda + 18.92g trisodium phosphate

Let’s convert weight to volume. We need to know the density:

Baking Soda: 2.2g/cm^3
Wash Soda: 2.54g/cm^3
Trisodium Phosphate: 1.62g/cm^3

Notice that the wash soda is much more dense than trisodium phosphate. You need a lot more trisodium phosphate if you’re measuring by volume.

Convert to volume:

g/density = cm^3 => 1.89g / (2.2g/cm^3) = (1.89/2.2)cm^3

(1.89/2.2) to (9.46/2.54) to (18.92/1.62) = .86 to 3.72 to 11.68 cm^3

1cm^3 = .202884 teaspoon

(.202884tsp/cm^3)x(.86 + 3.72 + 11.68cm^3) = .17tsp + .75tsp + 2.4tsp

Rounding to .2 to .75 to 2.4 teaspoons

My formula by teaspoon:

1quart water + .2tsp baking soda + .75tsp wash soda + 2.4tsp trisodium phosphate