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Did you know that you could preserve the flowers from your wedding or other memorial flowers so that they last for a lifetime if some care is taken? I did not know it until a few months but wait, it is not just the flowers; you can freeze dry most food. So if there are any seasonal fruits or other food that you wish to store for a long time, go ahead and freeze dry. The flavours are completely packed within the food, so you need not worry about losing its taste.
Freeze drying, otherwise called Lyophilisation is a process used in many fields like pharmacy, food processors, museums, taxidermy, floral, botanicals as a method of preservation and also in labs as laboratory lyophiliser. In modern days, it is being widely used in the floral freeze drying industry to preserve wedding bouquets and other flowers from memorable events like anniversaries, proms, graduation, special holidays, to the celebration of the birth of a child and more. We will look at the history, principle and the different stages involved in the freeze drying process.
Floral freeze drying is a method by which flowers are preserved in 3D by a process in which they are frozen at a temperature of -50 OC and then subjected to sublimation where the frozen water trapped in between the petals leave in vapour form without melting or causing damage to the flowers. We will look at the floral freeze drying process along with the various steps involved, caring for the freeze dried flowers and also some basic tips for freeze drying flowers.
Although freeze drying flowers and other modern deliberate preservation methods for flowers have been developed recently within the twentieth century, flower preservation has been in practice since centuries ago. Evidence of this are the flowers found in Egyptian tombs that are believed to be around 4,000 years old, flowers found along with bones of pre-historic man etc, which indicate that flower preservation methods had been in practice even before thousands of years.
Flowers have been used for various purposes like, jewels, ornaments, decorations and also for communicating. Different flowers and their colours carry different meanings and express different emotions. In general, flowers play a significant role in making important days and occasions beautiful and memorable.
Floral freeze drying is a very popular and modern business where flowers are freeze dried in 3D form. Flowers from various occasions and events, especially weddings, where they wish to have their wedding bouquets preserved as a keepsake. Anyone who has an interest in flowers and working with flowers will find this business very therapeutic. Flowers can be freeze dried also for interior decorations.
In earlier days, flowers were either dried in natural air or by pressing or using silica gel. Flowers dried using silica gel look very pretty with their 3D structure preserved. People who wish to preserve flowers as a hobby can take up the silica gel method to dry flowers, but if you wish to work for others, and help people keep their mementos from special occasions from drying away or getting spoiled, you will have to go for the freeze drying machines that are used to freeze dry flowers. Using this method, you can freeze dry wedding bouquets and other flowers, you can make freeze dried confetti from a mix of flower heads that were freeze dried or a mixture of petals that were freeze dried. The advantage of this method is, they come in original colours and textures and are biodegradable.
Floral freeze drying gives better results if the flowers are fresher. Flowers that are up to a week old can be freeze dried with good results, but the fresher, the better. Floral freeze drying was a widely used method first in the United States during the early 2000s.
What is Freeze Drying or Lyophilisation?
Freeze Drying or Lyophilisation is a process that is accomplished by sublimation of ice in vacuum. Sublimation is a process where solid ice changes into vapour form without melting.
What is the principle behind Freeze Drying (Lyophilisation)?
In this freeze drying process water / ice is removed from frozen botanicals as water vapour, with the help of deep vacuum. There is minimal or no shrinkage, thereby resulting in perfect preservation of original botanicals. This water vapour is collected as condensed ice.
How does Freeze Drying (Lyophilisation) work?
The flowers or other botanicals that need to be freeze dried are first frozen. The temperature of the frozen material is gradually increased to stimulate sublimation. This is done by placing the frozen items under deep vacuum. In this process, the ice crystals in the flower or botanicals sublime into water vapour which moves into and is collected in a condensation chamber over a period of few days where it turns into ice. This chamber is then defrosted in order to remove the moisture that developed during freeze drying. When the load is dry, condensation stops and ice formation stops in the condensation chamber. This is an indication that the freeze drying process is complete. The whole process can take between ten to twelve days, but also depends on the type of item and the quantity of items freeze dried.
The freeze drying process:
The floral freeze drying process involves freezing the flowers initially to around -50 oC in a chamber. Once frozen completely, vacuum is applied to this chamber and this will reduce the pressure around the flowers thereby lowering the boiling point of water, which will help it to vapourise at a lower temperature. So any frozen water trapped in the flowers in between the petals will vapourise by a process called sublimation. The frozen ice leaves the flower in vapour form without actually melting or damaging the flower. The resulting flower looks original with its original 3D shape and colour preserved.
In cases where bouquets need to be freeze dried, the flowers in the bouquet are taken apart after taking detailed notes about the construction and a picture. These flowers are then sent through the freeze drying process.
Freeze Drying Overview
What are the different stages in the Freeze Drying (Lyophilisation) process?
The complete freeze drying process consists of four different stages:
Pre-treatment: Flowers are pre-treated using pre-treating solutions. These solutions help with preserving the natural colours and increase its durability. These solutions also open the cell structure of the flower thereby aiding with the removal of water from the flower easily.
Freezing: This is a very important stage in the freeze drying process. The flower should be frozen below its triple point. The triple point is the lowest temperature at which the solid and liquid state of the flower can coexist. It is this temperature maintenance that helps with the sublimation process in the primary drying stage below. The usual freezing temperature for flowers is -25 oF
Primary Drying: At this stage, the frozen flowers are placed in the floral freeze dryer. The floral chambers are placed under near perfect vacuum (near perfect vacuum because perfect vacuum cannot be achieved). The sublimation process takes place, where ice crystals in the flower sublimate into water vapour without melting the flower.
Secondary Drying: In this process, the unfrozen water molecules in the flower are removed. The temperature is gradually raised to reach about 70 oF. Now any water remaining in the flowers change into water vapour and leave the flower tissues. This results in perfectly dry and preserved flowers.
Presentation of the freeze dried flowers:
The freeze dried flowers are not so strong like the original flowers, although they may look like the original. The freeze dried flowers are fragile and can break easily or get damaged easily if not stored safely. Moreover, moisture in the air can be absorbed back by the dry flowers and they can get spoiled and not stay dry as it was supposed to. So these flowers need to be protected by placing them in a frame or a display case, where they will be free from human touch and free from contact with moisture in the air.
In cases of bouquets, the freeze dried flowers are then put together following the notes and then mounted in a frame or case as requested or required.
Life of freeze dried flowers:
The flowers will last for a lifetime if they are looked after properly. Most freeze dried flowers are kept in cases that are protected by special glasses that have UV filter. Hence these flowers will be protected from UV damage. In order to preserve the colours of the flowers and foliage, they can be painted with floral tint.
How to choose and prepare flowers for drying?
- Pick fresh flowers from the garden in the morning just after the dew has evaporated
- For natural air drying process, pick up less mature flowers whose petals are not fully opened, as flowers bloom during the drying process.
- Remove leaves from the lower stem keeping a few at the top near the flower.
- Do not leave cut flowers in sunlight, as this can degrade the colours of the flowers
Uses of Freeze Drying flowers (Lyophilisation):
- Used in homes and offices for interior decoration
- Can keep flowers from important events as memories forever
Preservation of freeze dried flowers and botanicals:
- Moisture should be prevented from entering the freeze dried product in order for the products to have a long life.
- They should be kept away from direct sunlight and excessive humid areas.
- They should be free from dust and other environmental factors.
Facts about Freeze Drying (Lyophilisation):
- Faster freeze drying will lead to blistering, shrivelling and shrinking of the items.
- Pre and post treating chemicals help preserve the natural colour and vibrancy of flowers and botanicals, stabilise the colour and increase the durability and longevity, improve shatter resistance of the freeze dried flowers
- It is a combination of science and art
- Some flowers like dahlias, daisies and chrysanthemums do not freeze dry well and they may need reconstruction after the freeze drying process.
- The whole process may take 4 to 6 weeks and sometimes 8 weeks.
Advantages of Freeze Drying (Lyophilisation) botanicals:
- Perfect method of preservation, helps keep memories alive
- Cherish memories beyond just a photograph.
- The colour, shape and fragrance are preserved
- The pre and post treating chemicals are water based, biodegradable, non-hazardous
- The process is easy and enjoyable
- The freeze dried product is a work of art and lasts for many years, for a lifetime if looked after well.
Points to remember:
Wash off any dirt, dust or debris stuck to the flowers
The complete freeze drying and preservation process at a glance from start to finish:
- The bouquet of flowers from the events are photographed from different angles and these will help with rearranging the flowers after the freeze drying process.
- A detailed list of all the flowers and other items and notes on their arrangement are noted down.
- Before the preservation process starts, in order to carry out effective freeze drying, the bouquet or the arrangement of special event flowers are disassembled. Any other items like bows, ribbons, pins, pearls, notes, etc are set aside and an inventory recorded. These items are stored in a separate place.
- The flowers are hydrated for around 12 hours by standing them in fresh water.
- Moisture is removed from the flowers and depending on the type of flowers, they are pre-treated.
- The pre-treated flowers are frozen in freezers for around 24 hours at a temperature of -25 oF
- The frozen flowers are taken out and placed in freeze dryers to start the preservation process. This may take anything from 10 days to three weeks depending on the type of flowers and quantity of flowers
- Some flowers show a slightly deeper colour after the preservation process. For example, white flowers may become creamy colour.
- The freeze dried flowers are then post-treated using shatter proof solutions to increase their durability
- The flowers are then arranged and mounted into a keepsake frame with all the extra items that were originally attached.
- The keepsake frames are maintained airtight and mostly fitted with conservation glass that is UV safe.
Dr Veena Jadhav Professor in Resource Management .University of Agriculture Sciences Dharwad .Karnataka INDIA on March 11, 2018:
Am interested to carry out the research in freeze drying of cult flower and foilages . Can i get the pre and post treatment solution.and taring programm please inform me .
Terrie Lynn from Canada on October 25, 2016:
I knew the basics of freeze drying. But this article is really eye opening. Thank you for such an informative page. Great job.
livingsta (author) from United Kingdom on September 07, 2016:
Hello Teaches12345, thank you for stopping by and sharing your thoughts. I didn't know either that there was a way to preserve flowers for a long time, like forever. This technique was totally new for me to read. I am pleased that this was helpful. Have a great rest of the week. :)
Dianna Mendez on September 04, 2016:
I can see how freeze drying flowers would keep the memory of many touching moments alive. I didn't realize the process was so detailed. Thanks for the education.