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One of the things I love about Resincrete is how smooth the finished pieces can be, even before you start sanding or applying a sealer.
But if you're hoping to achieve a beautiful, professional-looking finish, there's often a little more work involved.
From smoothing rough edges to choosing the right sealer, I've discovered that the finishing stage can make quite a difference to how a handmade piece looks.
At Curious Cast Studio, I've experimented with different sanding techniques, gloss sealers, UV resin and even spray varnish.
Some methods have worked beautifully. Others have left me battling brush marks, streaks and the occasional mysterious piece of fluff!
In this guide, I'll share what I've learned about sanding and sealing Resincrete, including the products I use and the techniques that have worked best for me.
If you're completely new to Resincrete, my Resincrete for beginners guide covers the basic materials, tools and casting techniques to help you get started.
Does Resincrete Need Sanding?
Not always!
One of the things I've found with Resincrete is that the surface usually comes out of the silicone mould incredibly smooth.
The type and quality of mould you use can also affect your finished piece. In my guide to silicone moulds for Resincrete, I share my experiences with cheaper moulds and what to look out for.
Unlike some other casting materials, I don't generally need to spend ages sanding the entire piece.
Most of my sanding is simply to tidy up the edges or smooth the underside.
Depending on the mould, you might notice a slightly raised edge, an uneven base or a few small imperfections.
These are usually straightforward to deal with.
However, it's important to remember that Resincrete needs to have hardened sufficiently before sanding. Being ready to remove from the mould doesn't necessarily mean it's reached its full strength.
Always check the manufacturer's curing instructions.
What Sandpaper Is Best for Resincrete?
Personally, I prefer using foam-backed sandpaper by hand.
I find it comfortable to work with and easier to control than ordinary sheets of sandpaper, particularly when smoothing the edges of smaller pieces.
I usually start with a medium grit to remove any rough areas, then move to a finer grit to smooth the finish.
View the Foam-Backed Sandpaper I Use on Amazon
You don't need to apply lots of pressure. Resincrete is generally quite easy to sand once it's properly cured.
I prefer taking my time and removing a little material at a time rather than risking damaging a finished piece.
My Tip for Sanding the Bottom of Trinket Dishes
If the underside of a trinket dish isn't completely flat, I find it easier to place a sheet of sandpaper flat on my work surface.
I then gently move the bottom of the dish across the sandpaper.
This helps me sand the base more evenly than trying to hold the sandpaper in one hand and the dish in the other.
Once I'm happy with the shape, I switch to a finer grit for a smoother finish.
It's a simple technique, but one I use regularly.
What About Air Bubbles?
Resincrete generally produces very few air bubbles compared with traditional resin.
However, I've occasionally encountered them, particularly when I've poured a mixture too quickly or when it's already starting to thicken.
Sometimes an air bubble only becomes noticeable after removing the piece from its mould.
Small imperfections on the underside can sometimes be improved with careful sanding, although deeper holes won't necessarily disappear.
I've even had a few pieces where bubbles or other imperfections mean they're not quite up to my usual standards for selling.
It's all part of working with handmade materials.
Should You Clean Resincrete After Sanding?
Yes!
Sanding produces fine dust, and you don't want that dust ending up trapped underneath your sealer.
Once I've finished sanding, I make sure the piece is clean and free from loose particles before applying any finishing products.
It's important to avoid breathing in sanding dust. Work in a suitable area, follow the casting powder manufacturer's safety recommendations and use appropriate dust protection.
If you use water to remove sanding dust, allow the piece to dry thoroughly before sealing.
Does Resincrete Need Sealing?
For decorative pieces, I generally prefer to apply a sealer.
Resincrete has a lovely natural, stone-like appearance, but its surface can absorb moisture and become marked if left unprotected.
A suitable sealer helps protect the finish and can also change the overall appearance of the piece.
Depending on the product you choose, you can achieve anything from a natural matt effect to a more polished, glossy finish.
Personally, I tend to prefer a gloss finish for many of my Curious Cast Studio pieces.
Colour can also make a big difference to the appearance of your finished pieces. In my guide to colouring Resincrete, I share my experiences with pigments, marbling and different colouring techniques.
However, the sealer I use depends on whether the item is plain Resincrete or has been decorated.
My Experience with JDiction Gloss Sealer
For plain Resincrete pieces, one of the products I use is JDiction gloss sealer.
View JDiction Gloss Sealer on Amazon
I've experimented with different ways of applying it, and this has probably been one of my biggest learning curves.
When I first started sealing my pieces, I tried using ordinary brushes and foam brushes.
Unfortunately, I wasn't always happy with the results.
Sometimes I'd end up with visible brush marks or streaks across the surface.
Other times, tiny hairs or pieces of fluff would find their way into the sealer.
There's nothing more frustrating than spending time making something lovely, only to discover a little hair stuck right in the middle of your glossy finish!
Larger pieces were particularly frustrating because I found that thicker areas of sealer could leave visible streaks.
Eventually, I started experimenting with a different method.
My Current Method for Applying Gloss Sealer
Rather than brushing the sealer over every part of the piece, I've been experimenting with dipping smaller Resincrete pieces into slightly diluted JDiction gloss sealer.
Once I've coated the piece, I use a very soft, fine mitt to gently remove and smooth out the excess.
For me, this has produced a more even finish than some of my earlier attempts with brushes.
It also helps avoid those annoying little brush hairs getting caught in the surface.
However, this is my own experimental method, not an official application technique from JDiction.
Diluting a sealer can affect its performance, so I wouldn't recommend changing the manufacturer's specified application method without checking that it's suitable.
JDiction recommends applying thin coats and using a soft brush or dampened sponge to help prevent streaks.
The important thing I've learned is that more sealer doesn't necessarily mean a better finish.
In fact, applying too much can sometimes create exactly the problems you're trying to avoid.
How to Avoid Streaks When Sealing Resincrete
From my own experiences, the biggest challenge has been achieving an even coating without leaving visible marks.
Here are a few things worth considering.
Avoid Applying Too Much Sealer
Thick coats can leave visible streaks, especially on larger, flat surfaces.
I've had much better results concentrating on an even, thin application.
Choose Your Application Tools Carefully
Brushes can be useful, but I've sometimes found that they leave marks or shed tiny fibres.
If you're using a sponge or brush, make sure it's clean and suitable for the product.
Check for Dust and Fluff
Even the smallest piece of fluff can become noticeable once it's trapped under a glossy finish.
I always think it's worth checking the surface carefully before leaving the sealer to dry.
Allow the Finish to Dry Properly
Follow the manufacturer's instructions for drying times and additional coats.
Applying another coat too early can sometimes cause problems, and different sealers have different requirements.
Can You Use UV Resin to Seal Resincrete?
Yes, provided the products and surfaces are compatible.
This is another finishing technique I use regularly at Curious Cast Studio, especially when I've decorated a trinket dish with decoupage or a printed DTF transfer.
If you'd like to try decorating your own pieces, my guide to decoupaging Resincrete trinket dishes takes you through the process step by step.
I often use JDiction UV resin for these projects.
View JDiction UV Resin on Amazon
UV resin produces a clear, hard, glossy coating once fully cured.
It's particularly useful when I want to protect a decorative design beneath a smooth, shiny surface.
However, UV resin is different from an ordinary water-based craft sealer.
It requires careful application, suitable protective equipment and proper curing under an appropriate UV light.
How I Apply UV Resin to Decorated Trinket Dishes
When I've finished decorating a Resincrete trinket dish, I sometimes use a thin layer of UV resin as the final protective finish.
I make sure the underlying decoration and any sealers are properly dry before applying it.
I then add a small amount of UV resin to the surface and carefully spread it across the design.
I like to check that the entire decorated area is covered evenly.
One thing I've noticed is that resin can sometimes pull away from certain areas of a decorated surface before curing.
If that happens, it can leave little gaps in the coating.
That's why I always inspect the surface carefully before putting it under the UV lamp.
I also check for air bubbles and deal with any I find before curing.
For bubble removal, it's safer to use a suitable non-flame method and follow the resin manufacturer's guidance rather than introducing an open flame near uncured resin or other craft chemicals.
Once I'm satisfied with the coating, I cure the resin using my UV lamp, following the product's recommended instructions.
The result is a smooth, glossy finish that helps protect the decoration beneath it.
Is UV Resin Better Than Gloss Sealer?
I wouldn't necessarily say one is better than the other.
They serve slightly different purposes in my crafting.
For plain Resincrete pieces, I often prefer JDiction gloss sealer.
For decorated trinket dishes, particularly those featuring decoupage or DTF transfers, I often prefer a clear UV resin finish.
It really depends on the appearance I'm trying to achieve and how I've decorated the piece.
UV resin also requires more safety precautions, so I wouldn't suggest it's essential for every beginner.
Can You Use Spray Varnish on Resincrete?
Yes, some compatible spray varnishes can also be used to finish Resincrete pieces.
I've experimented with spray yacht varnish and found that it can produce a lovely glossy finish.
However, it's not always the most convenient option.
Spraying can be messy, the smell can be quite strong, and you need a suitable protected space to apply it properly.
Spray varnishes can contain flammable solvents and produce vapours or fine spray mist that shouldn't be inhaled.
It's important to follow the specific product's safety instructions, including using suitable ventilation and protective equipment and keeping it away from ignition sources.
For me, this makes spray varnish less convenient than some of my other finishing methods, particularly for smaller indoor crafting projects.
How Long Should You Leave Resincrete Before Sealing?
This is something worth distinguishing from demoulding time.
I generally remove my Resincrete pieces from their silicone moulds after approximately 30 minutes.
And if I have time, I sometimes begin decorating them soon afterwards.
I've had good experiences applying decoupage to freshly demoulded pieces.
However, sealing is a slightly different matter.
A piece can be firm enough to handle while still containing residual moisture.
Before applying a finishing product, particularly one that needs a dry surface, it's important to follow the casting powder and sealer manufacturers' instructions.
For UV resin especially, I would recommend making sure the surface and any decoration underneath are thoroughly dry.
Common Resincrete Finishing Problems
Through experimenting with different methods, I've encountered a few problems worth watching out for.
Uneven or rough bottoms: These can often be improved by sanding the base carefully on a flat surface.
Visible brush marks: I've found these can happen when applying gloss sealer, particularly if the coating is too thick.
Hairs and fluff in the finish: This has been one of my frustrations with certain brushes and applicators.
Air bubbles: These can occasionally appear in the original casting or within a coating.
Uneven UV resin coverage: Sometimes resin can pull away from parts of a decorated surface before it's cured.
None of these necessarily means you have to give up on a piece.
Sometimes changing your application method or working more carefully can make a noticeable difference.
My Advice for Beginners
If you're just starting to work with Resincrete, I wouldn't recommend buying lots of different finishing products immediately.
Start by getting comfortable with your casting material and making a few simple pieces.
You might find that the surface is already smooth enough and only needs a little sanding around the edges.
When you're ready to experiment with sealing, try a suitable product on a small test piece first.
This gives you an opportunity to practise your application method before working on something you've spent ages decorating.
And don't worry if your first attempts aren't perfect.
I've spent quite a bit of time experimenting with different techniques, and I'm still finding ways to improve my finishes.
Final Thoughts
Sanding and sealing might not be the most exciting part of creating Resincrete pieces, but they can make a real difference to the finished result.
I've learned that Resincrete usually doesn't need an enormous amount of sanding, particularly when using good-quality silicone moulds.
For me, the bigger challenge has been finding a sealing method that produces a lovely, even finish without brush marks, streaks or trapped fibres.
I've had good results with JDiction gloss sealer for plain pieces, while UV resin has become one of my preferred finishes for decorated trinket dishes.
I'm still experimenting, and I'm sure I'll continue discovering new techniques along the way.
But if there's one thing I'd recommend, it's this:
Take your time with the finishing stage. A little extra care can make a big difference to how your handmade piece looks.
Happy crafting!
Curious Cast Studio
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