Floral Preservation Casting (& Silica Gel tips) for Beginners

Updated: Nov 11

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 craft. ;)


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, 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 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.

Heating thicker viscosity resins in their bottles ahead of time, can help with bubble reduction as well. Be aware heating resin in bottles will reduce work time once product is mixed. If you are using a resin that is very low viscosity, there is no need to heat the bottles as the heat will not make it any more viscous than it already is.

Casting resins are most often lower to medium viscosities, and are often used in floral preservation projects. Casting epoxy resins are often a 2:1 ratio, but there are 1:1 casting resins 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 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).

Many floral preservation artists love working with the lowest viscosity casting resins, 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.

FLORALS MUST BE DRIED for best results

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 is similar to the consiseancy 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 out using other methods, but the key is they must have zero moisture left in them for best results in resin. 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. 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 so weeks. This may take some trial & error to get right. Activia has a general guide for drying time on some flowers on their website.

Tip: If you put an oversize layer of cheese cloth 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 cheese 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 cheesecloth is used), while lifting and gently sifting 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. 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.

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. 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. You can also order dried flowers online.

Be prepared that florals may change colour once added to resin, or when subject to any UV/sun.

If you get bubbles on the sides of your mould, try sliding something (can use a plastic toothpick) 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.

Be careful not to bruise your 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. This becomes a personal choice with experience.

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 preservation, but most suggest it is not necessary. Hairspray is typically not recommended as it may cause yellowing or discolouring. Some types of sealing products can burn delicate florals, but resin can if not careful as well. Some people only spray their lighter coloured florals to help with UV protection. Some people will actually paint the petals a bit (with colourfast medium) first so they keep & hold a vibrant colour if they dried with colour loss.

Keep in mind it is possible some organics possibly may cause discolouration. 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 yellow or gold in castings often reflect a yellow glow through the resin, so if using those colours, you may find a yellow glow throughout the resin piece.

Dandelion burst info:

If trying to do a dandelion burst, spray it very lightly, not too close, with an acrylic sealer or type of sealer (although 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).

Floral Preservation 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" (or preferred depth for space desired), let it set a bit. Then add & arrange your florals, then pour a thin layer gently over your florals and let that set. If adding more florals at this point, 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 pour). 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 cliamate.

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 (& 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.