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Floral Preservation Casting (& Silica Gel tips) for Beginners

Updated: May 18, 2023

Floral casting does take some practice and experimenting, so do plan to try a few pieces first before making an important keepsake. Patience will be needed when learning this artform. ;)

I have a few examples in other blogs, for reference, using the iCoat epoxy products.


There are numerous options with floral casting resin products. There are many many epoxy resins with different features, and people have different preferences for each project. It is important to use the right type of epoxy resin for the type of projects you are going to create.

Top-coating resins (often a 1:1 ratio), often have too thick of a viscosity for many floral casting projects, so are not be ideal for best bubble release. Top-coating resins are typically meant for 1/8” depths (up to max of 1/4”), per layer. Most floral artists do not use or recommend top-coating resins in their deeper floral preservation art projects. Top-coating resins can be used however in shallow moulds, (such as coaster or tray moulds), or if user is prepared to pour in numerous shallow layers, and being careful to pop bubbles where possible. Pouring a resin too deep in a mould (then what each resin max recommendation is), can cause numerous issues including, can cause a pre-mature exothermic reaction and overheat your resin, and burn the flowers, and cause mould to fuse to the resin as well (ruining your mould).

Heating thicker viscosity resins in their bottles ahead of time, will help with bubble reduction. Be aware heating resin in bottles will reduce work time/pot life once product is mixed. If you are using a resin that is very low viscosity (ie: iCoat Depth, iCoat TP21), heating the bottles will not make it any more viscous than it already is, but does help bubble reduction. If the bottles are cold, they should be brought up to minimum of warm room temperature ( 76F/24c or a bit higher), before mixing. Use an infrared temperature gun to be sure, & aim it down the neck of the bottle for most accurate temperature reading of the liquid. Each epoxy has different best temperatures to work with, so never assume one is the same, or will work the same as another.

Casting resins are most often lower viscosities (though there are some medium viscosity), and these are best for use in floral preservation projects. Casting epoxy resins are often a 2:1 ratio, but there are 1:1 casting resins (such as iCoat CE4100HV), as well. The 2:1 ratios tend to have the thinner viscosity, which offers better bubble release. However, just like mentioned above, you can heat the bottles of the casting resins that are medium viscosity to help make them more viscous, which helps to reduce bubbles.

Deep pouring casting resins come in a variety of ratios depending on brand. They can be 2:1, 3:1 or even 4:1 ratios. The iCoat Depth we carry, is a 2:1 ratio. The deep pour casting resins degas much easier, so are great for, and developed for use in deeper pour type projects, but the downside is they often take a lot longer to cure. Deep pour casting resins are not suited for thinner layer type projects. Too thin layers (for type of resin) will take a very very long time to cure. Although, after initial resin layer is set & flowers are set in place (so they don’t float), a deep pour can often be used to fill the balance of the mould (project & depth dependent), or at very least to reduce number of layers required.

Many floral preservation artists love working with lower viscosity casting resins, or good bubble release options (such as iCoat CE4100HV), since no pressure pot is needed for stunning & clear results. For best results view and practice the instructions for keeping bubbles to a minimum prior to pouring.

Important tip: When dealing with someone else's (irreplaceable) flowers, floral preservation artists typically like to work in 1/4” to 1/2" (depending on resin & mould), pours per layer, wherever the flowers are exposed to the resin. When using organics/florals in moulds, the epoxy brands suggested maximum depths, are for when not including organics/florals. So, when adding organics/florals, you will likely not be using the maximum suggested depths of an epoxy, except maybe once you are past the area of the mould that flowers are. That said, some people have tested using deeper pour layers on their own florals first, to see if they can pour deeper with some types of epoxy (such as deep pours).


FLORALS MUST BE FULLY DRIED all the way through. All organics being used with epoxies need to be completely dehydrated. Any possible moisture can cause issues.

You do need to ensure that when you are using organics such as florals, that they are completely dried out, and have no moisture remaining prior to casting in resin. If they are not dried out, they may turn colour or brown inside the resin, and possibly eventually rot. Silica gel is often the preferred way to dry flowers. Although called a gel, silica we use in our floral art, is similar to the consistency of sand.

One product often used (& available in Canada), is called Activia Flower Drying Silica gel. Often sold at Michaels, Walmart, Staples & online. (Tips on reactivating silica below). You can also dry florals/organics using other methods, but the key is they must have zero moisture left in them for best results in resin.

July 29/22 - Editing to add, Michaels Craft Store (in Canada), now also carries another option, by Ashland (flower drying silica).

Start with about a 1/4"- 1/2" of silica gel in the bottom of a sealable container, then gently & slowly add more silica until fully covered. Put the lid on to seal well. If lid doesn't seal well, the silica can pull moisture from air outside container (causing need to reactivate the silica sooner then necessary). Follow directions for the product you're using to dry flowers. Depending on the size & thickness, and moisture of the flowers/organics, they could be dry in 3 days up to 3 or more weeks. This may take some trial & error to get right. Activia has a general guides for drying time on some flowers on their website. If in doubt, leave it a bit longer.

Tip: Gerber daisies, (petals often fall off in silica), leave in silica for a handful of days and then take out and put them just on top of silica, with only silica on top in the centers.

Tip: If you put an oversize layer of a cloth (tule) with holes in it (acts as a strainer) in the bottom of your container (overlap the sides of container), before adding silica, it is helpful with lifting all the flowers out easily as well (especially the tiny ones, and petals that fall off). The overlap edges of the cloth can be folded inside container, once ready to put container lid on. Then when it is time to remove flowers the overlap acts a bit like handles (if enough cloth is used), while lifting and gently sifting (straining) the florals/organics out of silica container.

Once your items are dry enough, gently remove florals/organics from silica gel sand, and use a soft cosmetic brush to carefully remove any residue that doesn't shake off. Another option is using air sprayed gently to remove any silica dust. Silica gel left on flowers in resin castings, can appear as bubbles. Note: when doing upside down castings (for example pyramid moulds), the silica often floats out of the flora to the bottom of the casting.

When project is unmoulded, and then is re-oriented towards the top, it will show all the silica that remained or floated out of the flowers during cure process. For this reason, people often prefer to use moulds that floral layout & design can be arranged face up, to alleviate worry of silica sand that may not have been removed.

If your studio/ workroom gets too cold at night, microbubbles may come up out of nowhere.

If there’s bit of a texture at the top, you may have a humidity issue. recommend getting a Bluetooth hygrometer to track your daily/nightly temp and humidity in your workspace. It's much easier to pinpoint certain issues!

They're cheap on amazon!

There are numerous ways to dry flowers/organics besides silica gel sand. Some people like to use something called a Micro-fleur drying product that dries flowers between a press in the microwave. It works for some, but others do not like that method as much. Some people claim that any heat drying (micro-wave) methods may not preserve the florals as nicely, since they feel you are cooking the flowers, and that can change colours of many sensitive florals. Flowers can be pressed between books (the old fashioned way) as well, in fact some floral artists prefer to dry this way with certain types of leaves or other organics being used in their projects, where they require item to be flat. As you get more experience, you may find you use different drying methods for different types of plants. Some people use dehydrators for florals, sliced fruits, veggies and other items you may want to put into your castings. You can also order dried flowers online.

Be prepared that florals may change colour once added to resin (they look permanently wet), or when subject to any UV/sun.

If you get bubbles on the sides of your mould, try sliding something gently (can use a plastic toothpick or silicone brush or spatula), along inside edge to pull bubbles off the edge & up, to take them out of the resin. Be careful not to scratch your mould doing so. Some people suggest spraying 99% alcohol on sidewalks if mould, to help prevent bubbles attaching to mould. Some suggest moving the mould carefully swishing the resin to assist bubbles moving off sidewalls, though this is not often a possibility due to delicate florals.

Be careful not to bruise or add oils to flowers by handling them without gloves. Oil from your fingers can sometimes transfer to the floral petals, and you may not see it prior to setting in resin, but it may show afterwards in the resin, looking almost transparent. Some people like to seal their flowers first prior to setting in resin, but most prefer not to. You do not need to do so, however some floral artists find it helps with less bubbles, and colour preservation. Some artists will dip their florals into resin first (gently pour resin into the flower over something else), then place it in the mould. This becomes a personal choice with experience. Do this carefully, so as not to break off petals.

If you are a floral preservation artist, you likely know to use gloves when handling customers florals, however prior to receiving bouquets, you have no control over how many people may have touched the petals in a bouquet (from the people picking them at a farm, to the florists making the bouquets, to the wedding day where it's often handed off to others). Just try to instruct your customers to be careful where possible for best preservation opportunity. While bouquet is not in use, keep it in a vase to protect it, and keep it upright when possible, try not to lay the bouquet down on its side.

Some artists like to use an artist grade spray lacquer (available at artist supply stores) on florals to help with dried preservation, there are sprays designed for florals as well, but many floral artists suggest it is not necessary. Hairspray is not recommended as it may cause yellowing or discolouring. Some types of sealing products can burn delicate florals. Some people only spray their lighter coloured florals to help with UV protection. Some people will actually paint the petals a bit (with a colourfast medium) first so they keep & hold a vibrant colour if they dried with colour loss. I have heard of some floral artists airbrushing dried florals back to it's original colour as well as needed.

Keep in mind it is possible some organics possibly may cause discolouration in resin. If you receive florals from customers, that may cause discolouration, it is best to find a way to seal those prior to casting. Another thing to keep in mind, is neutral, yellow or gold in castings often reflect a yellow glow through the resin, so if using those warmer colours, be prepared you may find a yellow glow throughout the resin piece (it is coming from the inclusions).


Floral Preservation Resin Process information:

When placing your flowers, there should ideally be resin in the mould first. Be careful not to push dried floral petals down or they may separate, break and end up floating. It's best to pour a thin layer often 1/8"to 1/4" (or preferred depth for space desired), let it set a bit. Then add & arrange your florals, and let that set. You can pour a thin layer gently over your florals at this time as well and let that set, if you prefer. If adding more florals, you may need to do another thin pour to get the new added florals to set in place (so they don't float to the top of fresh resin layer).

Once flowers/organics are in desired location & secured with previous resin layers, you can then decide based on your resin brand directions, how deep your following layers will be. With some florals, and some resins, if it's too deep a pour, you can accidentally burn your flowers if the resin overheats from being poured to deeply in a mould at one session. This is why many floral preservation artists work in layers only. Or, another option is once your florals are set, you can use a deep pour for the balance of the mould, as it will not get hot enough (provided pouring in the brands recommended depths), to burn the florals. There is not one set of rules or timing or depth unfortunately. It all takes practice based on your environment (temperature and humidity), resin type, volume per layer, size of mould/project and inclusions being used. Start with smaller projects, and get to know how your resin will work with varying scenarios that effect the projects, in your environment. Often a person in a dry climate will have completely different results than a person in a humid climate.

Another important factor to note, if you are working in a mould that is more enclosed (such as a sphere mould), they tend to hold in more heat (as resin heats up to cure), so you will need to pour in shallower layers than you would in wide open moulds that can release the heat easier.

Ideally figure out your design, prior to setting in resin. Some people prefer to work in the mould placing florals face up so they can see the design well as they go. This is actually easier for bubble release too & doesn't show (any remaining) silica as much either. Some moulds require you to work with top of piece facing the bottom (like some sphere's and pyramid moulds).

If you're using glitters, they may sink to the bottom (unless they're very fine glitter), while flowers float to the top, so you must plan in advance for different additives. And if you're not sure, you may need to practice on a smaller scale with different additives as well to learn how they all work in the type of project you are planning.

Releasing Bubbles:

When it comes to popping any bubbles, there are many schools of thought. Some prefer to use a (long neck style) barbecue lighter, and carefully hold it so flame is about an inch above the resin and mould. Never let flame touch your resin or mould, as you can accidentally fuse your mould to the resin piece, or singe your resin. Some people like to to use a light spray fine mist of 99% isoprophyl alcohol to pop their bubbles instead of a torch. Caution though if you use too much alcohol, it can effect your finish &/or cure. Also if your resin is far enough in cure process, the alcohol may create tiny pinholes in finish So don’t spray too late.

Once piece is removed from mould, there is sometimes a need to top-coat or dome-coat a piece or sand & polish it. It is easier to dome coat some pieces than others, depending on the item shape. This is something each artist often develops a personal preference on as well.

You may find information on finishing ideas & options helpful... please see separate blog posts about:


Note regarding your finished masterpiece;

Upon completion of your floral art projects, keep in mind they are all individually hand crafted, making them different and unique. They are not going to be machine perfect. Bubbles can get trapped in, on & near florals, or on edges, and sometimes dust particles jump on, and while we try greatly to minimize them, they are a natural, unavoidable part of handcrafting. Some pieces might not have completely straight edges, and most sharp edges will have been hand sanded & buffed off. Colour of flowers and resin can fade or change over time too (like many hand made art pieces). Instruct customers to keep them out of direct sunlight to help prolong it's life.

For cleaning all resin pieces my preference is to use a damp microfibre (or very soft) cloth, followed by the microfibre glass buffing cloth to dry/buff it (or a dry microfibre cloth). On finished pieces, please avoid use of glass cleaners or any disinfectants that may contain alcohol. Alcohol can break down the finish. If soap is required, use mild dish soap & water.


SILICA GEL info and tips....

If your Activia silica gel sand has lost all its blue colour, then it is time to reactivate it. Once the blue crystal colours are gone, it will no longer absorb moisture well from the flowers, and flowers may just go mouldy in your sealed containers instead. Depending on how much moisture the silica has absorbed, you may get 2-3 uses out of the silica prior to needing to recharge/reactivate them again. While it is time consuming, it is well worth the added time to always be sure it is fully reactivated/dehydrated, so that the silica can do it's job as effectively as possible with your flowers (organics).

To reactivate the Activia Silica Gel Sand, place it in a shallow pan in the oven, heated 250 degrees Fahrenheit, for no less than 5 hours. The pink and white crystals will return to blue when it is ready to be used again (dehydrated). The oven method seems to be the preferred method over the microwave method based on numerous floral preservation artists experience. If you have a lot of silica sand, look for the big 12 x 20 x 4" stainless steel steamer trays from restaurant supply store, and stir often during the drying process.

There are no fumes from the silica itself when recharging it in the oven, but it is necessary to wear a particulate (dust type) mask when moving the silica from one container to another. The dust, if inhaled, is very bad for your lungs. Most floral preservation artists use their regular oven, and allow the silica to fully cool before transferring it back in to sealed storage containers. Silica gets very hot, so do not transfer until it is cooled. Keep in mind you don't want to leave it out too long, as that allows it to partially re-hydrate and lose some drying efficiency.

If your storage containers do not fully seal, you may need to reactivate your silica more frequently. Double bagging with zip-lock bags is okay for a month or two, but if you are not going to use it immediately, it's a better idea to put it in a glass jar with a good seal. For example, The gallon size restaurant jars are an option for storing the silica gel sand. Another option to store silica sand when not in use, is to have several large ziplock bags full, stored in a large airtight box container.


Dandelion burst info:

If trying to do a dandelion burst, some people spray it very lightly, not too close, with an acrylic sealer or type of sealer. Sealing is not a necessity, many people cast them without sealing too. Fill mould about 1/4' of the way with casting resin, then place dandelion puff on top. Let it sit for 4 hours, then gently pour more resin around the sides until it's fully encased in resin (for a mould size between 3 to 7 cm).

Pyramid Mold info:

If creating a floral piece in those large 6"h pyramid molds, be prepared it may take about 9 layers to the top. For your first several times, pour in 1/2" layers max. Once you are past all the florals, you can pour in deeper layers (as per brand suggestion).

If using iCoat CE4100HV casting epoxy, use an infrared thermometer to check temperature of resin in mold has returned back to about 80F before adding next layer.


If you're planning to preserve others floral keepsakes, make sure you draw up a contract. The contract needs to cover every thing! Let customers know about potential of floral colours changing once in resin, discuss that while you try to minimize bubbles, they can & do still occur, discuss payment arrangements, shipping arrangements, etc. Make sure they've agreed to your contract terms before starting any work. You could add a line in the contract that states, by sending your flowers to me, you are confirming you have read and agree to all my shop policies, and FAQ's. Then make sure your shop policies and FAQ's cover everything too.

Let customers know it is SUPER important to know if it will be a fresh bouquet vs dried they will send you. Fresh flowers require roughly 10lbs of silica gel, many containers to hold it all while dehydrating, extra space and other materials ordered ahead.

For shipping florals to you, you might want to ask them to take apart the whole bouquet(s) and wrap each flower separately or in bunches. You may want to ask them to wrap the stems of the flowers in damp kitchen paper towel, and then foil. Then package carefully in a tupperware type box, and use the dry kitchen towels or other soft shipping items to completely but gently fill all empty spaces in container. If they have any other items they'd like as inclusions (charms, ribbons, small mementos), they should put them in a waterproof zip lock bag to include in the package for you. You will need to figure out and agree on the best shipping option that will get it to you safely and quickly.



ArtWorks Resin Canada

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