Most people are aware that Romaine lettuce (which many people use for Marror) must be insect free. It may be purchased pre-washed and checked, or you may clean and wash it yourself. Romaine lettuce hearts are relatively clean and not difficult to render insect-free. I will include my suggestions for cleaning a few common vegetables and strawberries at the end of this post.
According to halocha something which is soaked in liquid for 24 hours straight is as if it had been cooked. To keep Romaine lettuce fresh after cleaning it and checking for infestation it is helpful to refrigerate the lettuce in a tub of water, which can keep it fresh for a week or more. While this is a very good idea, if it was soaked for 24 hours it cannot be used for Marror. This is not a problem on the store level as the water spray that stores use to keep the lettuce or horseradish root fresh is not problematic.
Vegetable Checking Guide – It is highly recommended that you attend a course or receive training from an expert and not rely on only reading the instructions:
Rav Moshe Feinstein said that we need not be concerned about a speck that it less than 1.3 mm if no legs, or wings are visible and it doesn’t move.
“Chazaka” checks for various types of lettuce and cabbage (where only a certain percentage of the produce is checked) are intended for Mashgichim who are checking very large amounts. It is not intended for “home” checking.
Equipment >
Until you become an expert in identifying insects you should use a jewelers’ loupe (available from Amazon for about $5) or a Smartphone app such as MagLightPro ($1.99) to help you identify insects. A lightbox (B & H Photo) or a LED light wand (available at FiveBelow for less than $10) should be used. A needle helps move spots on the thrip cloth so that you can see them from different angles. Mashgichim like Dawn liquid dish soap at two tablespoons per gallon of water. Vegi-wash with a hechsher may be used at TRIPLE strength in place of liquid soap if necessary. You can sandwich the thrip cloth between two colanders so that the thrip cloth stays in place. For Pesach make sure that whatever you use is Kosher for Pesach.
Cannot be cleaned: Brussel sprouts, blackberries, raspberries, and mulberries. They may be used only if they are grown in insect free conditions.
Commercially washed salad (such as Spring Salad Mix of Coleslaw Mix) that does not have reliable supervision:
Place the contents is lukewarm water and mix for 30-60 seconds. Pour the water through a thrip cloth. If there is no infestation you may use the salad. If there is even one insect or worm the entire contents must be washed with lukewarm soap water – 2 tablespoons per gallon and agitated for a minute. Rinse repeatedly and check the last rinse water with a thrip cloth. If it is clean soak the vegetables in plain water for at least 15 minutes to remove any remaining taste of soap. If there is any infestation the soap washing process must be done over.
Romaine lettuce hearts, spinach leaves, cabbage, and other leafy vegetables:
Separate the head into leaves, cut and separate, or shred and separate. Wash with lukewarm soap water – 2 tablespoons per gallon and agitated for a minute. Always use enough water so that the vegetables will be washed well. Open any tight areas that may not allow water to enter. Rinse repeatedly and check the last rinse water with a thrip cloth. If it is clean soak the vegetables in plain water for at least 15 minutes to remove any remaining taste of soap. If there is any infestation the soap washing process must be done over.
Strawberries and organic blueberries (regular blueberries and grapes just need normal washing):
Wash with lukewarm soap water – 2 tablespoons per gallon and agitated for a minute. (Remove the tops so that you won’t have to clean and inspect under each stem individually.) Always use enough water so that the berries will be washed well. Rinse repeatedly while swishing vigorously in the water. Check the last rinse water with a thrip cloth. If it is clean soak the berries in plain water for at least 15 minutes to remove any remaining taste of soap. If there is any infestation the soap washing process must be done over.
Broccoli and Cauliflower:
Separate the head into small sections that will allow the soap solution to penetrate. Vigorously shake each section in hot soap water – 2 tablespoons per gallon (which can be touched). Agitate all of the broccoli in the soap solution for a couple of minutes. Rinse repeatedly with lukewarm water and agitate. Always use enough water so that the vegetables will be washed well. Check the last rinse water with a thrip cloth. If it is clean soak the vegetables in plain water for at least 15 minutes to remove any remaining taste of soap. If there is any infestation the soap washing process must be done over.
I usually have reusable thrip cloths available for sale in stock.