How to detect a marked deck

How to detect invisible ink marked cards? Many people are curious be this.
Some magicians are using marked decks for great magic shows. They may be worried about others knowing the way to break their magic shows while the audience have great interest in it.
As for the marked cards being used in poker games, some guys know about it but they just can't detect it. Thus the secret to detect marked cards is very important and necessary in protecting people from gamble cheating.
Know more is always better.
The marked cards refers to the playing cards that are with invisible ink marks on the back. Usually the IR or UV contact lenses and sunglasses can see the invisible marks clearly, and that's what people use in the poker games for cheating.
What can we detect the invisible juice marks without the contact lenses?
Firstly, you can just put the doubted marked decks with the clean playing cards. If they have color difference. At least one deck of them has problems.
Secondly, put the poker decks under the sunshine. There would be marks on the marked deck and you will see it with the sunshine.
Thirdly, Money detector with purple light can check the invisible ink marks. You can just check the decks with money detector if you doubt about the decks.
Just try these methods and you can check the marked decks for sure if they are marked.