One of the best things about epoxy resin is that you can preserve almost anything — from flowers, photographs, shells, glitter, wood, and pigments.

But not everything belongs in resin. 

Some materials introduce moisture. Others release air, discolor over time, or even prevent your resin from curing properly. If you've ever wondered why a project became cloudy, sticky, cracked, or filled with bubbles, the material you embedded may be the reason. Here's what you should avoid putting in epoxy resin, and what to use instead. 

1. Fresh Flowers

Flowers are one of the biggest causes of failed resin projects. Because they're full of moisture, they continue releasing water after being embedded. This often causes: 

• Cloudiness
• Browning
• Mold growth
• Air bubbles
• Poor curing

Better option? Always use fully dried or professionally preserved flowers before casting them in resin. 

2. Wet Wood

Wood and resin are a beautiful combination, but only if the wood is dry. Fresh or damp wood can:

• Release moisture into the resin
• Create bubbles
• Warp after curing
• Cause cloudy spots
  

For river tables and larger woodworking projects, allow lumber to dry properly before pouring. 

3. Leaves, Plants, and Organic Materials That Haven't Been Dried

In case you haven't guessed it yet, all things need to be dried before being placed in resin. This also applies to:

• Leaves
• Moss
• Pine needles
• Herbs
• Grass

Organic materials contain moisture that continues escaping during cure. Dry everything thoroughly before embedding. 

4. Food

People often ask: Can you put fruit in resin? Technically...yes. Should you? Usually no. Fruit, vegetables, bread, certain candy, and other foods contain water and sugars that eventually break down inside the resin. 

Even if the project looks good initially, it may discolor, shrink, or grow mold over time. 

5. Damp Paper

Paper works beautifully in resin, but only when it's completely dry. Printer paper, photos, tickets, maps, and artwork can trap moisture or absorb resin unevenly. 

For best results:

• Seal porous paper first if needed.
• Allow any inks or paints to dry completely.
• Avoid paper that has gotten wet or wrinkled. 

6. Oily or Greasy Objects

Resin doesn't bond well to oily surfaces. Avoid embedding objects coated with:

• Cooking oils
• Wax
• Grease
• Lotion residue

Clean objects thoroughly and dry before pouring. 

7. Objects That Trap Air

Some materials naturally contain tiny pockets of air. Examples include:

• Pinecones
• Bark
• Cork
• Driftwood
• Porous stones

As resin cures, trapped air escapes and forms bubbles. Better option? Seal porous materials with a thin coat of resin before your final pour. 

8. Items That Melt Easily

Epoxy resin generates heat while curing. Large pours can become surprisingly hot (especially in the summer months). Avoid embedding materials that soften or melt easily, including:

• Thin plastic
• Foam
• Wax
• Low-temperature adhesives

If you're making a deep cast, use a resin specifically designed for thick pours to reduce excessive heat buildup. Using the wrong resin or pouring too thick can create excessive heat during curing. 

9. Anything Dirty

Dust. Sawdust. Pet hair. Lint. These may seem obvious, but contamination is one of the most common causes of disappointing finishes. Always wipe embedded objects clean before pouring. 

10. Incorrect Colorants

Not every color works with epoxy. Avoid adding:

• Water-based paint
• Acrylic paint in large amounts proportionate to your resin volume
• Unkown craft products
• Excessive alcohol

Too much moisture can interfere with curing. Instead, choose colorants specifically made for epoxy resin, such as resin dyes, mica powders, or resin pigments. You can see our list of recommended colorants here.

11. Objects That Can't Handle Heat

Many beginners don't realize resin creates heat as it cures. That means delicate items like:

• Some plastics
• Thin vinyl
• Certain adhesives
• Heat-sensitive decorations

These can all warp or deform during curing. If you're unsure, test a small sample first. 

12. Anything You Haven't Tested

This may be the most important advice. Every material behaves differently. Even experienced resin artists test new inclusions before committing to a large project. A five minute test can save hours of work, and an expensive batch of resin. 

What Destroys Epoxy Resin?

People often ask what actually damages cured epoxy. The biggest causes include:

Excessive UV Exposure

All epoxy resin will gradually amber over time. Premium formulas with UV inhibitors slow the process but cannot eliminate it completely. This is the formula we recommend for the highest level of UV protection and quality - Studio Series Epoxy Resin. 

Extreme Heat

Leaving cured epoxy near very high heat can soften the surface or reduce its lifespan. 

Moisture During Cure

Water and humidity don't usually ruin cured epoxy, but moisture introduced while the resin is curing can cause cloudy finishes and surface issues. 

Incorrect Mixing

Improper measuring or incomplete mixing is still the number one cause of sticky resin. 

Final Thoughts

One of the best parts of working with epoxy resin is the ability to preserve and showcase meaningful objects, but choosing the right materials is just as important as choosing the right resin. 

As a rule of thumb, if an item is dry, clean, stable, and non-porous, it's usually a good candidate for resin. If it's wet, oily, dirty, or heat-sensitive, it's worth taking extra precautions, or leaving it out altogether. 

A little preparation before you pour can make the difference between a flawless finish and a frustrating do-over.