RDT Ross Droplet Technique Spray Coffee Beans Spray bottle

What is RDT? 'Ross Droplet Technique'

What is RDT?

RDT or 'Ross Droplet Technique' refers to when you apply a small amount of water to you dose of coffee prior to grinding.

This added moisture reduces the static build up in your grinder and significantly lowers the amount of retention.

RDT for Coffee Beans Wet water on coffee spray coffee beans grinder

Coffee Fines when grinding RDT

While this does make grinding coffee much cleaner, particularly when grinding washed coffees or using electric grinders. There is another school of thought that highlights how using RDT removes more particles from your grinder, this is particularly negative when you are switching from espresso to filter roasted coffee as you can experience more of these particles come through.

As well as this Coffee fines can be an issue, when grinding coffee with out RDT and then using RDT we experienced much more fines present in our ground coffee and was able to taste this in our cup of coffee. 

However it's not all bad news, We found that when you use RDT on every dose of coffee there was a happy medium. This reduces the mess and lowers the fines, making the grinding experience much more enjoyable.

Different Methods

When it comes to RDT the principal is the same but there are a couple of different techniques used.

The first is the cheapest / most accessible method. To do this, simply fill a cup with water and dip the back of a spoon into the water and then into your dose.

The largest issue with this is that you run the risk of toppling over a cup of water and that it doesn't necessarily look the best on your coffee bar.

Another popular method of using RDT is by using a spray bottle, We have a 50ml metal spray bottle that is a convenient size and removes the need for a cup of water with a spoon. The RDT Spray bottle can also easily be taken with you when travelling.


When considering using RDT for your grinder it is important that you get in touch with the seller / manufacturer and ask 'is RDT ok for this grinder'. 
Some burrs are made from material that is prone to rusting and other grinders have components that are prone to rust so by making sure and confirming this with the manufactures gives you peace of mind.

Last thing you want is to get a rusty burr set or broken hand grinder.

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