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What is a Refractometer and Why Do I Need One?

Refractometers are used for quite a lot of things — drug diagnosis, gemology, veterinary medicine, aquarium upkeep and farming.

In gardens and farming it is an all-in-one tool that can be used to test the health of your crops, via a brix rating system. A refractometer uses refractive light passing through plant sap or fruit or vegetable juice to take a reading of nutrient levels. A high rating is good news for your crops — they should be healthy, disease and pest resistant, high in nutritional value and you’re likely to have a good harvest. A low rating means that your crop will not grow to its potential due to some external limiting factor, such as: a dilution of its nutrients due to high nitrate content, a mineral imbalance in the soil allowing weeds to flourish and take from your harvest, a low calcium content in the soil or a low/steady boron reading indicating an issue with the translocation of sugars within the plant.

The refractometer is a cheap and effective way to take the guesswork out of growing, by giving you a scientific guide as to the health of your crops and an indicator on what to do to make them grow to their potential. It has no moving parts and is simple and easy to read — it is a gauge using a numbered scale. It is one of the most valuable measuring tools we can use in our systems.

You can order hand held refractometers here.

14 Comments

  1. Whilst refractometers may be an ideal way to examine the sugar levels in your produce, a much more effective method of analysis is through Chromotography an explanation of which can be found here https://www.biodynamics.in/chrom.htm Chromotography is very cheap at approximately US$1.00 per soil test. It is not the sugar levels of your produce you need to be testing but the overall health of your soil and the microbial content therein. Once this is in good order, the sugar levels of your produce will be well taken care of.

  2. Kia Ora, It is my understanding that the brix of plant sap is a reflection of the health of the soil. A plant can not grow to be a strong healthy plant (you can not necessarily tell by the eye) without having access to the right minerals in the right relationships.
    If you have an imbalance or something missing you will not achieve high brix growth.
    I find that a refractometer is an extremely useful instant tool, no tests have to be sent away for measuring, no on going costs. I am committed to be growing high brix food and seeds because i understand that human bodies need complete (complex) carbohydrates, complete proteins,and high quality fats and phytoalexins to be fully nourished, and maintain our health and our DNA.(Check out Deep Nutrition by Catherine Shanahan) These things do not exist in low brix food. Food that is low brix(under 12 approx), contains simple sugars which in nature is food for the insects and fungi. being able to use a refractometer to take an instant test of where your plants are at has helped me understand and grow my biological agriculture systems far faster than any other way I have found. It is critical to understand how to use them effectively. It is not just a matter of doing 1 test. You must test on a regular basis, at the same time of the day , because sun affects the result, and plants send around 30% of their sugars to their roots over night so the levels will be lower in the morning. There are other things you must watch for too. Buy a refractometer that has good instructions for home gardeners so you can see what needs to be taken into account. You will be more likely to find it useful!!!!!!

  3. You need to give your plants the best possible soil to grow in. If you are doing this – then what help is either a refractometer or chromatography? If you say it will increase your efforts to build better soil then don’t wait for the results – do it now.
    We need to avoid systems that complicate a simple process, Provide the best possible conditions for healthy growth of your food – you can do no more.

  4. Hello Kay

    I don’t think anyone is disagreeing that a brix reading is valid and a refractometer probably useful.

    However, I see it as the difference between getting to know your soil by actually seeing and reading its composition via do-it-yourself chromotography at $1 a shot – no sending away for tests or much in the way of ongoing costs and great self-satisfaction in reading and remediating your soil but which takes 2 days instead of instant gratification – or, $140 odd for a refractometer that is going to provide a reading and not much else. Perhaps, once you have your chromotography done and dusted, the refractometer may well be a useful, albeit expensive, tool.

  5. A Refractometer gives you an instant reading on scale so not only can you gauge the nutrient density of your crop plants and trees but also if the readings go up on the scale after you apply your natural soil food fertilizers you know you are not wasting your time and you are not doing unnecessary work.

    I bought my first refractometer for $350 in 1991 and have used it 1000s and 1000s of times and it still works exactly the same as the day I bought it because there are no moving parts and it will still be working in a 100 years time probably. It fits in my pocket and I can take on consultancies easily. This little very efficient tool has enabled me to increase soil fertility with the minimum of effect and increase crop nutritional value over a larger area and help many people to do the same.

    Chromatography does not use a scale – it measures the eutectics of patterns by judgement and can involve very complicated equipment see https://en.wikipedia.org/wiki/Chromatography

  6. Refractometers vs Chromatography may be more a matter of what you like to use. Refractometers fit in your pocket, are pretty easy to use, and give an instant reading…wonderful!

    Chroma takes more set up, more education/training and you need to order the materials from specialist laboratory suppliers. Chroma gives you a ‘printout’ and physical ‘picture’ that can be explained and shared later. Some people like one and some people like the other. I suggest that both work and both take practice to understand the readings.

    The good news is that we have ways of measuring plant vitality so we don’t need to rely on lab testing,this means we have direct ways of knowing that what we are doing aids plant vitality and soil health.

    Being able to make instant tests in the field using a refractometer means that you can test more often and more easily… paul taylor

  7. Yes Paul, you are right on there man. As for complications, if a poor Mexican or any other South American farmer can use chromtography then it can’t be too darn complicated. There is little point in the addition of ad hoc amounts of natural soil food fertilizers if you do not need them or, the problem is somewhere else in the soil. I see the refractometer as a tool to be used to check on what you have done after doing the chromotogrophy. More of a check to see that you have the result you were going for.

    I would commend all to participate in a course with Eugenio Gras just to understand the process and to see just how simple it is and the lack of any complex equipment outside of a hole punch, filter paper, a 1″ nail to roll the wick the bottom of a milk bottle, a plastic lid and a syringe. Not what you would call complicated. Eugenio teaches simplicity and practicality and the elimination of expensive soil tests. It is DYI and idiot proof.

    1. “……if a poor Mexican or any other South American farmer can use chromtography then it can’t be too darn complicated…”

      Wow, just wow.

  8. Just a note: A good tool should be used a lot and we depend on it more and more, I believe a quality refractometer is worth the cost.

    Sergi: Eugenios work is great, and the chroma is very useful for bio fertiliser testing etc etc, just realise it takes a bit of setup and a kit of specialist equipment. One of the good things about both tools is that you can be completely illiterate and still use them with a bit of practice. Ultimately these tools are a way of directly ‘communicating’ with your plants.

    Another thing to recognise is the power of empowerment, when you use these sort of tests, you have tools that you can use to directly measure the result of your trails and share that knowledge. We need more trails and more knowledge sharing. There is talk of starting up a sharing site called ‘food for free’ and start sharing some chroma tests, and some refractometer testing along with some bio fert trails, composting ‘secrets’ etc etc.

    paul taylor

  9. Hi all, a late comment on this story. Users of refractometers should be aware that they are only of use if the user has a database of previous readings for comparison. High brix (sugar %)readings can indicate minor through to severe water stress as a lack of water concentrates the sugars. So a high reading, contrary to indicating a nutrient boost, could equally be indicating a lack of water or simply a change in water supply. Refractometers have been used as a tool for watering schedules in tree plantations.
    I have one and use it to determine the time to pick my wine grapes. A sample from the vineyard is tested and historical harvesting data tells us what brix level will produce optimum wine flavours and alcohol levels. An unripe grape will read around 18 while a ripe one will read 26 and an over-ripe over 32. Before refractometers people would just taste the grapes, which is still done, but the refractometer allows a sample of grapes at different ripeness to be tested as a group. As I get more experience with my vines I need the refractometer less and less.
    cheers,
    Jamie

  10. I’m totally new to this but it looks interesting to use a refreactometer for an experiment with vegetables and biochar & EM I would like to do. This way I prob also could measure the plants health apart from its growth.

    Questions concerning purchasing one:
    – most simple which model do yo use and recommend?
    – There are digital ones and optical ones..
    – There is a refrectometer for solid and liquids which one do you use?
    – Do yo use digital or visual one?
    – Furthermore there are several scales used Brix, Oechsle scale, Plato scale, Baumé scale. Are these all present on each refractometer?

  11. hello all
    please help me
    i want to know. can i measure leaf color or leaf sugar?
    and totally tell me about every thing i can use the refrectometer?
    every one know send me manpaizam (at) gmail.com thanks u

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