What is pot life, open time and wet tack?
Pot Life
This is the useable life of an adhesive sitting in a bucket once it has been mixed. Some adhesives will begin to set in the bucket quicker than others, due to their different chemical makeup and reactivity. Atmospheric and climatic conditions can also affect the pot life of a mixed adhesive.
Should the useable "Pot Life" of an adhesive be over, and the product is setting, do not mix in more water or polymer to rejuvenate it. Discard it, and mix a new batch.
Open Time
This is related to "Wet Tack". Once the adhesive is spread on the floor with a notched trowel, there will come a time where the "Wet Tack" has disappeared and the tile will not adhere well to the spread adhesive. The adhesive will have a skin formed on its surface.
Should the "Open Time" have expired, scrape off the spread adhesive and discard it. Provided the "Pot Life" is still good, apply new mixed adhesive with a notched trowel
"Open Time" is a mandatory test under the European Standard, and draft AS 4993. The testing under ISO 13007 requires all cement, dispersion and reaction resin adhesives to undergo this test.
Adhesive is spread, and tiles placed into it at 5 minute intervals. To pass the test, the tiles bedded into the adhesive at 20 minutes after spreading, must resist the minimum prescribed tensile force after curing. If open time extends beyond 30 minutes, then the adhesive is accredited with an "extended open time" and the letter "E" appears in the performance classification.
Wet Tack
Once the adhesive has been spread the "Open Time" begins. Always ensure there is sufficient "Wet Tack" prior to bedding tiles into the adhesive.
A good test for "Wet Tack" is to spread your fingers and place your fingertips into the adhesive. If the tips of your fingers come out with adhesive on them then the "Wet Tack" is sufficient. If the come out without adhesive on them, then it is likely the adhesives "Open Time" and "Wet Tack" has expired, and therefore the adhesive should be removed, discarded and re applied with fresh mixed adhesive.