How to Sand and Polish Epoxy Resin to a Mirror Finish - Step by Step Guide

One of the questions we are asked most frequently by our customers is 'How to effectively flat and polish epoxy resin?', we've created a full-length pro-guide in the shape of a video tutorial and thought it would make a great Instructable too!

Whether you are creating coffee tables or serving boards right up to countertops or boardroom tables this process shows how anyone from hobbyist to professional can achieve incredible results and finish their project to expert standards.

Our previous Instructable DIY Resin River Table Using Clear Epoxy Casting Resin and Wood demonstrates the flatting and polishing technique but this Instructable gives the topic its full attention and shares lots of hints and tips along the way to achieve great results first time.

The step-by-step video tutorial and Instructable covers the complete process of how to flat and polish epoxy resin up to a high gloss/mirror finish, including tools, abrasive selection, process and professional tips.

Hope you enjoy it and please let us know what you think, we'll happily answer any questions or comments you may have .....

The wood and resin slab that we demonstrate the flatting and polishing process on was made using GlassCast 50 Resin which had been machined using a router after it was fully cured to a course surface in preparation.

Flatting

An Orbital Sander (DA) in 125mm or 150mm with dust extraction outlet

Sanding Discs to fit your sander in a range of grits - from 120 grit to 1200 grit - the amount of pads you will need depends on the quality of the abrasive pads - we used 1 disc from each grit over a 0.25sqm panel.

A marker pen

Water in a spray bottle and a microfibre cloth

A high quality dust mask which you will need to wear throughout the sanding process

Danish Oil

Polishing

A Polisher - with variable speed settings

125mm Backing Plate for your Polishing Pads

Medium/Hard (Orange) Polishing Pad

Fast Cutting Compound

Soft Wavy Black Polishing Pad

Ultra Gloss Polishing Compound

Microfibre Cloth

The single most important aspect with sanding and polishing is to be consistent and systematic in your approach. Without the systematic and consistent method, it is all too easy to miss steps and undo all your hard work on previous stages. Often it is only later in the sanding and polishing process that the shortfalls show through so using a good method from the start will save you time later on.

The technique is pretty much identical regardless of the project, however the starting grit can vary depending on how rough your starting surface is. If the surface is very rough (ie: machine routed) you will need to start off at the coarsest grit - 120. If the surface only has minor scratches or surface defects you may be able to start off with an 800 grit abrasive

The most important thing to remember is that you sand off enough surface material at each grit stage, by completing enough passes with each grit in the correct way.

A pass consists of:

• Sanding from left to right with an overlap and working down the length of the part AND then sanding vertically top to bottom
• Each movement should overlap the previous move to ensure the surface is sanded evenly
• We completed between 5 and 7 passes with each grit (as shown in the tutorial)
• Each grit level takes approximately 10 minutes

Tips:

1. Use a marker pen between each pass to put some random marks on the resin. we'll explain the reason for this in the next step
2. Regularly check the discs for clogging and remove and unclog the discs as needed
3. You will know if your disc is clogged if you can see circular scratches forming on the resin which look like pigtails
4. Unclog the disc by removing and flexing it between your fingers to remove the resin dust. Eventually the disc will need to be replaced as it becomes more difficult to unclog
5. Regularly clean the resin surface by wiping it and check progress to see that the scratches are being removed. If necessary do some additional passes before moving onto the next grit

Coarse Grit Sanding

If the surface is rough we start with the most coarse grit and progress through the stages as follows:

• 120 grit paper - 5 passes
• 180 grit paper - 5 passes
• 240 grit paper - 5 passes
• 400 grit paper - 7 passes
• 800 grit paper - 7 passes

Between each pass clean the surface using the cloth and water spray and use marker pen to make a squiggle and write the pass number to remind you how many passes have been made.

The purpose is that with each complete pass, the pen marks will be removed. If the pen marks remain, slow down the sander and/or press down a little firmer to ensure there is enough cutting being done with each pass. After each grit level check the surface and there shouldn't be any marks or pen showing - if there is repeat passes and thoroughly inspect the surface to make sure that the scratches from the previous grits have been removed. Go back and sand further before moving onto the finest grade.

Fine Grit Sanding

For the final stage of sanding before polishing, use a 1200 grit paper and complete 4 passes.
At this stage, to help prevent the paper clogging, before starting and between each pass spray a mist of water on to the resin surface. Don't use the marker pen during this grit level as the ink could mark the wood or resin when mixed with water.

When the 1200 grit level is complete, give the surface a thorough clean and allow it to dry off before progressing to the polishing stage.

As a final step before polishing, it is worth sealing the bare wood - this will prevent the wood being stained by the polishing compound, we used a couple of layers of Danish Oil.

The polishing process:

We use a two-step process with two products to achieve the mirror shine:

1. Coarse cutting compound
2. Ultra-gloss polishing compound

The main bulk of the work in this stage is done using the cutting compound and is diminishing abrasive. This means that it gets finer the more it is worked. If you want to achieve a higher gloss we used an ultra-gloss polishing compound to take the surface to the incredible mirror finish we achieved.

Start by affixing a medium/hard foam pad to your polisher and a few blobs of the compound to the resin surface, then using the polisher (whilst still turned off) spread the polish evenly over the surface.
Now turn on the polisher, on a slow speed setting and make passes over the surface whilst applying a medium amount of pressure and follow the left to right and up to down over-lapping movement.

Complete three passes in total for this stage - applying additional compound for each pass, making sure that you allow the compound to entirely diminish before moving on to the next pass.

Tip: occasionally check to see if the resin is warming up. If it feels slightly warm that's ok but if it feels hot to the touch allow it to cool before proceeding.

To achieve a mirror finish like we have done, change the polishing pad to a soft pad and using a high-gloss compound add a few blobs to the surface and spread around with the polishing machine (turned off) before turning the polisher on to a medium speed and medium pressure and complete two passes on the resin.

Finally, using a clean microfibre cloth, wipe the surface clean and buff with the cloth.

That's how to polish epoxy resin to a mirror finish!

The surface looks amazing and the shine is like glass. The process is hard work and time consuming but is worth the work for the incredible result!

Don't forget its possible to achieve great results by had if you are working on resin jewellery for example but the same principles apply - working through the grits, cleaning in-between levels and finally polishing.

We would love to hear what you think and we're happy to answer your questions and comments and hope this shows that the mirror shine is achievable for everyone.

Thanks for reading our Instructable :-)