Perfume Making With Essential Oils: Top notes are what you smell first, but they last the shortest amount of time. Use roughly 20-40% of top notes in your recipe. Middle) Middle notes are the backbone of the blend. They help to bring it all together without leaving any sharp edges. Use about 40-80% in your blends. Base) Base notes are the ones that last the longest and give a deep and rich scent to the blend. Use about 10-25% in a blend.