WHAT CAUSED THE GRAY FILM
MAC is a mild acid cleaner made of phosphoric and hydrochloric acid specifically for tents. Long term tent rentals such as vineyards, universities and special event centers leave the tent for months and sometimes all year round. The rain and even dew moisture that settles on the top of the tent eventually begins to leave a “gray” film. This is basically hard water film and mineral deposits. This is similar to drinking glasses develop chalky-looking films and have to be soaked in vinegar, also an acid. Vinegar has a pH of around 4.5. MAC has a pH of around 2.5. That makes it roughly 20 times more acidic than vinegar. However, the tent vinyl being a petroleum product is totally unaffected by it. and the “gray” film comes off leaving the vinyl looking like new.
IS THE “GRAY” FILM MINERAL DEPOSITS OR POLLUTION?
The “gray” films can also be caused by pollution. This may be caused by factories, car exhaust, even fires. All of these may be miles away. but settle on the long-term tent. So always test your “gray” tents to see if it is mineral deposits or pollutants that cause the film. Lay a section of the worst part of the tent top out. Make two bowl like indentions of about 3”. Make the two “bowl” indentions close as possible together so that you can compare. Pour straight MAC in one “bowl” and straight Citro in the other “bowl”. After about 15 minutes take a dry cloth and wipe out both “bowls”. Whichever one leaves the 3” “bowl” the whitest should tell you the make up of the “gray” film.
IF IT IS A MINERAL DEPOSIT FILM DO THIS
Once you determined it is a mineral deposit film, take a pump-up garden sprayer and mix the MAC. In a two gallon sprayer add 10 ounces of the MAC and fill the rest of the sprayer with water. That will make about a 1 to 30 mix. However, MAC can be mixed much stronger and it will not harm the tent viny. IT WILL, HOWEVER, MILDLY CORRODE AND DISCOLOR THE GROMMETS AND THE BUCKLES. This is usually a minor concern to get the tent white again. Always spray on to a DRY tent! After about a few minutes you can brush the acid around to keep it from puddling and keeping the high spots wet with the MAC. Usually, after 20 to 30 minutes the film should be removed. You can now damp mop rinse the tent.
IF IT IS A POLLUTION FILM DO THIS
Once you determine the Citro did a better job of removing the film, you will need to use the Citro straight, undiluted to remove the film. You will need a solvent resistant garden sprayer. Citro will eventually dissolve the o-rings and gaskets in the sprayer if it is not solvent resistant. Spray the undiluted Citro onto the DRY tent fabric. You should brush with a push broom or use a floor machine with a WHITE pad. A red pad will start to dissolve and leave a pink film to rinse off. Also, if your shoes have a black sole that is not solvent resistant they will start to dissolve and leave a blackish film. After a thorough, light scrubbing, you should be able to see the film being removed. You can then damp mop rinse with water.