Bonus Module – Specific Gravity

Natural Perfumery Institute

Specific Gravity

Introduction

Basic Course students: This is an edited version of one of the three modules in the Intermediate Course. I feel it is necessary to teach the basics of specific gravity to you, and hope you will continue on to study at the Intermediate Level. After 12 years (2019) teaching students, I realize that this information can help them in their perfumery pursuits. I am not including the Excel.xls workbook that the Intermediate Students receive because it typically includes a lot of interaction with questions back and forth, and this is not included at the Basic Course level.

Be aware that this bonus module, the study of specific gravity, is not included in any other online/distance-learning course for natural perfumers. I want you to understand these basics as it will help you.

From the Intermediate Course Module 1

In the basic natural perfumery course textbook, you were given an introduction to specific gravity (SG) with an illustration of a photo of kaffir lime oil in one flask, and allspice berry in another. You observed that although both weighed 20g, the volume was quite different.

The dilution exercise you learned in Module 1 allowed you to standardize the drops you were using to make mods and perfumes. Specific gravity wasn’t an issue there; the volume of the drops was the important factor and keeping them uniform. If you placed 20g of the same oils, but in their diluted form, in beakers, they would measure evenly, not showing the difference in volume shown above. That is why you cannot just ‘scale up’ your mod numbers using drops, you need to convert the diluted numbers into undiluted, weighed aromatics. This core module will instruct you no the next step up in technique: learning how to convert those standardized drops to the proper weight, in grams, to make large batches of perfume.

By large, that may mean from several ounces up to gallons – typically the limit for artisan perfumers. However, if you ever go into large-scale production, this method and the accompanying Excel spreadsheet will work on any volume of perfume you wish to make. You will now be able to move from working with diluted drops to measuring out undiluted aromatics, the most professional way to blend perfumes.

Materials needed

 

o   Graduated cylinders

o   Scale

o   Aromatics

o   Excel spreadsheet for blending (supplied) (not supplied in this Bonus Module for Basic Course students)

Note: Graduated cylinders have much more precise measurements than beakers. They are typically shown in 1ml increments. You can typically find sets of them from 10ml to 1000ml. I suggest 10, 50 and 100ml.

 

graduated cylinders

graduated cylinders

Photo source: Karter Scientific Glass

 

Step One: Specific Gravity and How to Determine It

  1. Weigh an empty 100ml cylinder
  2. Record the weight of the empty cylinder (for reference)
  3. Hit the Tare button
  4. Pour the essential oil or absolute into the cylinder
  5. Record the weight of the essential oil or absolute
  6. Divide the weight by 100
  7. You now have the specific gravity of that oil

specific gravity calc

As a formula:

Note: See the next section for weighing smaller amounts.

Weighing Smaller Amounts of Aromatics

We need to weigh out a known volume to be able to calculate the ratio of the benchmark, so if we have a known volume of a material, e.g. 2ml of rare pricey EO, or solid/semi-solid absolutes and concretes. A 10ml graduated cylinder is best for this exercise.

You would pour in an EO or absolute or concrete, (warming the absolute or concrete so it can be poured into the cylinder), reaching the 2ml line, and then weigh that amount. Say it would weigh 1.94g.

So we need to take that known volume – 2 ml – and get back to the 1:1 ratio. So we divide that weight by 2 to arrive at the 1 ml volume/ratio.

Therefore, 1ml of that material would weight 0.97g, and because we know the benchmark ration is 1:1, we divide 0.97 by 1 to arrive at a specific gravity also of 0.97.

Most SGs are express to the second decimal point, the graphic formula and numbers are shown for those who wish to be extremely precise. I have found that two decimal points work fine, but I do prefer to use three for greater precision.

On the MSDS and COA sheets you read for the basic course, you will see that often the specific gravity is displayed as a range of numbers. For example, the specific gravity of lemon myrtle is indicated to be between 0.895 – 0.915 @ 20°C. This is not to confuse you, it is to show you that as aromatics can vary in scent from year to year, from distiller to distiller, so can the specific gravity. It is up to you to either get the specific gravity for your aromatics from your supplier – or confirm they are not using old SG numbers, they must have the ones specific for your oil – or conduct the SG calculations yourself. I recommend conducting your own measurements; it is a great skill for a perfumer to have.

Step Two: Determine the Cost of the Aromatic

Cost should be determined per gram. This may fluctuate, according to the amount you purchase, so you may find yourself adding two entries for some aromatics. For example, in March, you purchase 10 ml of rose otto and pay a high retail price per gram. In September, you join with some other perfumers and purchase 100 ml, and receive a wholesale price. Enter both in the spreadsheet, so you can keep precise records of costs as you move from one purchase price to another.

You need to review the amount of aromatic you purchased to confirm the price per gram. Check with the supplier regarding this. Most are now selling by weight, not volume, especially if they are a large supplier. There is a difference between the UK (EU) and USA measurements. You can use the conversion software found here https://joshmadison.com/convert-for-windows/  for volume measurements.

Screenshot of Josh Madison conversion program:

convert screenshot

 

Step Three: Transfer Information to the Excel Master Blending Sheet

  1. Open the copy of the original Master Blending sheet.

excel blending sheet

  1. Enter the relevant information in the columns. The botanical name, Supplier, Lot and Batch are optional but encouraged. You can sort alphabetically, taking care not to highlight beyond Column W.
  2. Learn to use the red triangles to open up the comment boxes. They will guide you through relevant cells and what is to be found there or worked on there.
  3. Each time you use an aromatic in a perfume, enter it into the Master Sheet. When you have time, weigh and convert all of your aromatics to specific gravity and price, but if you don’t have time, just concentrate on the perfume ingredients you need right now.
  4. Save and close the Master Sheet.
  5. Open it and now save it with the name of the perfume you are converting from drops to grams.

Step Four: Create a Perfume Using the Master Sheet

First: Decide the amount of perfume you wish to make, and enter it in cell 66G. I suggest a small amount at first, perhaps an ounce, until you get familiar with the spreadsheet.

Second: Enter the strength of the perfume you wish to make in cell 67G. Most perfumes are 20-30%, EdPs are a lesser percent, EdTs even lower. You can refer to your textbook for guidelines. You may find that 20% is strong enough for a perfume, especially if you use many high-intensity aromatics or accessory aromatics.

Don’t enter anything in cell 68G, you will work without adding water at this time.

If you are using tinctures, for example, ambergris or hyraceum, go to the Materials (Sheet 2) and find the value there, and enter the name in cell 43A. If using more than one, enter the second in cell 44A.

Column A: Enter the names of your perfume’s top notes here. Read the red arrow comment. A foolproof way to correctly enter the name of the aromatic is to use the dropdown menu or highlight, cut and paste the name from Column P. Determine which method is easiest for you.

Column B: Read the comment in the red arrow box, and enter the percent dilution you used in your mod for the perfume.

Column C: Enter the number of drops from your mod sheet.

Column D, E, F: These contain hidden data and are not shown.

Column G: I do not use this column because I do not blend my mods with ml or grams, but it is included for those who may.

Columns H, I, J (K is hidden), L and M will now show the calculations performed by the spreadsheet.

Using the techniques for weighing aromatics that you learned in Module 1, weigh out the aromatics in small beakers, one at a time. I use a selection of 50ml beakers for this purpose. As soon as an aromatic is weighed, transfer it to a jar that is of the size you need to make the amount of juice your determined on the spreadsheet and put on the lid. Follow this for each aromatic, until all of the aromatics are in the jar. This is now your compound base for the perfume.  Add the amount of alcohol indicated on the spreadsheet, stir the compound and alcohol, and you now have juice. Cap the jar tightly and place it in a cool, dark place to age, occasionally stirring the juice. When it is mature, chill, filter, and bottle.

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