Actually, I have heard that using a shop or shopkeeper to determine decay is even more exact and reliable, but as I do not own one I am not sure how that method works
That is correct.... I placed the instructions on how to do it on entropiawiki.com a long long time ago already.. the reason why the shop/shopkeeper method is the most accurate is because any person with a calculator can easily see all the decimal places and then subtract it from the remainder after one use.
Just remember to move the decimal place over two places when inputting the information into entropiawiki.com otherwise it would be incorrect.
edit: here is the information that I entered in from entropiawiki.com in case you can not find it...
Shop/Shopkeeper method
General Information
This method of decay testing is 100% accurate of the other tests. It works by subtracting the initial value from the final value of TT in order to obtain the difference (decay value). This test requires at least two uses left on the item and does not need to be at FULL TT.
How to do it
Place your item into a Shop/Shopkeeper.
Check on the price listing as if you are going to list it up for sale. This will show you the EXACT value of TT you have left on the item. Make sure to record this number down exactly as it appears.
Take the item out of the Shop/Shopkeeper and then use the item ONE time.
Place the item back into the Shop/Shopkeeper.
Check on the price listing as if you are going to list it up for sale. This will show you the EXACT value of TT you have left on the item. Make sure to record this number down exactly as it appears.
Take the initial value that you had and subtract it from the final value to obtain your decay value. Example: 5.00 (initial TT value) and 4.9821000 (after use TT value) 5.00 - 4.9821000 = 0.0179
To add this value from the example (0.0179) into entropedia, move the decimal place over to the RIGHT, TWO places like so: (1.79)
~Danimal