Frequently Asked Questions epoxy

Below we answer frequently asked questions. Epoxy is a great material with great potential. Our customers have many questions though in daily practice. We try to give some more clarity here. Do you have a question that is not listed here? Please let us know.
Problems and solutions
Applications and processing
Tips & Trics

What is epoxy?

Epoxy is an exceptional hard and tough chemical resin. It contains superior qualities concerning suture and resistance against water, chemicals etc. Epoxy is formed out of a chemical reaction between the two components (resin and hardener).

Epoxy sticks to virtually any underlay, provided that the underlay is well cleaned and grease free. Epoxy doesn't stick to polyethylene (for example garbage bags), silicone and teflon. The suture on ABS is reasonable.

General formulas and calculations


Rectangle: length x width
Circle: pi x r x r 
Triangle: (height x basis)/2


Rectangular ba: length x width x height
Tube: pi x r x r length
Piramyd: (basis x height)/3


Circle: pi x diameter


1 liter = 1000 ml. = 1 dm3
A square box of 100 x 100 x 100 cm has a volume of 1.000.000 cm3 = 1.000 dm3 = 1 m3


Weight: volume x density
Density: weight/volume
Volume: weight/density

Repairing osmosis

Before you start repairing osmosis, make sure that the ship is not too moist. There are special hygrometers to test this on polyester.

There are 2 possibilities:

1. There are only a few local vesicles found:

Sand the vesicles open and rinse them well with sweet, clean water. Then let it dry well. The formed small hole can be filled with Mr.Boat epoxy putty. Then apply 4-5 layers of epoxy on the repaired spot.

2. Vesicles are found all over the ship:

When this is the case, you have to remove the gelcoat. This can be done with a special peeling machine or by sanding. Then the ship is thoroughly rinsed with sweet, clean water. Next the ship has to dry very well, otherwise there is a good chance the osmosis will recur.

A first layer of epoxy will be applied on the dry laminate (possibly injection epoxy when loose fibres are visual). Imperfections can be puttied. After that 4-5 layers epoxy are applied.

Can I make a fuel tank of epoxy?

Our standard Mr.Boat epoxy is less suitable for this. We do supply a special epoxy with a high chemical persistence. If you want more information about this, please contact us.

What is epoxy used for?

Mr.Boat epoxy has many applicatiins. Floors are made with epoxy, air planes, car parts, aquarium back walls, boats etc. Mr.Boat epoxy is mainly used to glue, putty, laminate or coat.

Mr.Boat injection epoxy is waterthin and used for strong sucking surfaces like for example end grain wood.

Mr.Boat casting/photo epoxy is a crystal clear, UV resistant epoxy perfectly suitable for casting objects in for example table tops.

Mr.Boat epoxy puttly is sold ready to go or you can make it yourself by adding fillers to the mix of Mr.Boat epoxy. Mr.Boat epoxy putty is a watertight, shrink free putty which is very light and well sandable.

Mr.Boat epoxy glue is used for diehard glue connections on most materials.

Handy formulas area calculation of ships

Below some handy formulas:

Underwater ship for a non deep stabbing (sailing)boat:
Surface area in m2 = 0,5 x length of the waterline x (width + depth)

Underwater ship for a deep stabbing sailboat:
Surface area in m2 = 0,75 x length of the waterline x (width + depth)

Surface ship:
Surface ship in m2 = (Length over all x width) x 2 x height waterline till deck

Surface area of the deck:
Surface area in m2 = (0,75 x Length over all x width) minus surface area of construction

Casting electric components

Epoxy does not conduct and can be used to cast electric components like for example LED's. You can use the standard Mr.Boat epoxy for this project. Do not cast more than 3 - 4 cm per time because of the heat release.

What is osmosis?

Osmosis is the symptom of arising vesicles on polyester boats which eventually can burst, with all consequenses. These symptoms usually occur on olders boats and often have to do with used materials and technics from that period.

You can recognize osmosis by sticking a hole in the vesicle. When damp comes out with a sour smell or feeling greasy, then it is osmosis. It is necessary to solvethis problem because it can aggravate quickly and it can even delaminate the polyester.

Further in these FAQ will be explained how te repair osmosis and how te prevent it.

I haven't used the epoxy for a while and it is hard now

This can happen when epoxy is stored for a longer period of time in a place with lower temperature. You can make the epoxy easily fluid again by putting the tank in warm water for some time. This has no effect on the quality of the epoxy.

Is epoxy strong?

Very very strong. Connections with epoxy fillets are much more stronger than the separate parts. Provided that the application is done properly, sustainability and toughness is imcomparable.

Creative applications with epoxy

Mr.Boat Epoxy is widely used by artists for many applications. A few examples are ennobling of pictures and paintings, creating (watertight) garden objects, art objects, case modding, jewelry and much more.

Check out our gallery for projects of our customers.

Remove cured epoxy

Heat the epoxy with a hair dryer upto a maximum of 90 degrees Celcius untill the epoxy gets soft again. Remove epoxy as much as possible with a scraper or putty knife. The remaining epoxy can be removed with sanding paper. Provide for enough ventilation when heating epoxy.

Releasing epoxy

Epoxy sticks to virtually anything but not to polyethylene. Garbage bags are made of that. Handy when you want to coat something but afterwards be able to remove your project from the underlay.

To make a ledge which later can be removed.

We also sell mold release wax. With this wax you treat a mold so that it can be released from the project afterwards.

Epoxy is thick and hard to process

Put the tank in some warm water for a while and it becomes fluid again.

What customers do with our epoxy

- Building and repairing boats
- Building aquaria and terraria
- Making back walls yourself
- Modelling
- Making Art objects or ennobling
- Repairing wood rot
- Making adjusted wheel chairs
- Building or rebuilding campers
- Car repairs
- Car tuning (make your own carbon parts)
- Casemoding
- Building (Kite)surfboards
- Building Longboards and skateboards
- Repairing fishing rods
- Repairing carbon window cleaning stem
- Epoxy floors
- Building wooden bathroom
- Making and ennobling lures for fishing
- Repairing (carbon)rods
- Mr.Boat epoxy is used in testing the Marsrover (really;)

Which epoxy should I use?

Removing non cured epoxy

This works excellent with white wine vinegar. Much healthier than the chemical substances. Available and sold in any supermarket.

A white, greasy layer forms on the epoxy after curing.

This is called "amine blush" and can arise when worked in a high humidity or when curing epoxy gets wet. Before any next layer is applied, remove the amine blush with water and a scouring pad, otherwise the next layer will not or badly stick.

Amine blush can arise too when epoxy is applied on a wet underlay. the recommended humidity percentage of wood is < 12%. To measure the humidity percentage accurately, you can use our handy hygrometer.

Amine blush can also be prevented by using peelply.

What is injection epoxy?

Mr.Boat injection epoxy is being diluted with special epoxy thinner, is waterthin and penetrates deep in the porous surfaces. Note that the strength and water tightness of injection epoxy is lower than the standard Mr.Boat epoxy. It is recommended to apply one more layer of the standard epoxy after applying the injection epoxy.

What's the difference between standard epoxy and epoxy castng resin?

Cast/photo epoxy is mainly used for decorative use. Think of casting objects, pictures ennobling, casting tabletops, making jewelry etc. This epoxy is crystal clear and UV resistant. Through its low heat generation during curing, is the cure time upto 24 hours at room temperature. The definite cure time kan take upto 5 days.

Cast/photo epoxy is not suitable for wood building/repairs. Ik could be used for aquarium back walls but the standard Mr.Boat epoxy works better (faster cure time, stronger).

For all applications where optimal strength is needed, standard Mr.Boat epoxy is used.

Extend cure time

After mixing poor the epoxy from a mixing cup into a paint tray. The epoxy is spread over a larger area and can be used longer. Also a lower temperature gives you more time to apply the epoxy.

Can I dilute epoxy?

Never dilute epoxy yourself. Use if desired Mr.Boat injection epoxy. This epoxy is diluted with special epoxy thinner, is waterthin and penetrates deep in porous surfaces. Note that strength and water resistance of injection epoxy is less than the standard epoxy. We recommend to apply an extra layer standard epoxy over the injection epoxy layer.

Another way to dilute the epoxy without corroding the mechanical qualities is to heat the epoxy (for example in warm but not hot water). The epoxy will become more fluid but watch out: the cure time will then be shorter as well.

Epoxy on wood gets dim

When the epoxy layer on wood gets dim, the wood is very moist. The ideal humidity of wood is < 12%.

" Craters" arise in the epoxy

The cause of this is greasiness. Epoxy departs on some spots. Solution for this is sanding again and decrease the bad spots well. Then apply another layer of epoxy.

Preparation of different underlays

Cured epoxy:
When amine blush has arised (white, greasy layer) rinse it first with water and a scouring pad. Then clean the underlay and decrease it. Sand it with grain 80.

Clean the underlay and decrease it. Sand it with grain 80.

Clean the underlay and decrease it. Sand it with grain 80.

Teak or "greasy" wood:
Clean with acetone for about 15 minutes before applying the epoxy in order for the grease to disappear and the epoxy to penetrate well in the wood. Make sure the acetone is evaporated before applying epoxy.

Porous wood:
Clean the underlay and decrease it. Sand it with grain 80. Possibly apply a layer of Mr.Boat injection first.

Clean the underlay and decrease it. Sand or sandblast untill the steel is as clean as possible. Apply directly after that a thin first layer epoxy to prevent flash rust.

Decrease and sand. Possible to pretreat with special aluminum primer.

Depending on the type of plastic. In most cases decrease and sand first. Epoxy does not stick to polyethylene, polypropylene, nylon, perspex and poly carbonate.

Suture on hard plastic types like ABS, PVC en styrene is possible provided that the underlay is well prepaired and enough surface to suture. After sanding you can shortly go over the surface with a gas burner to improve the suture. Watch out: do not melt the plastic!

When you are not sure about the origin of the underlay, work with a sample first to make sure it works out well for the rest of your project.

To make epoxy glue or putty in wood colour

To finish unpainted wood, you might want to keep the original wood colour. Mix the epoxy with saw dust untill the desired thickness and finish the wood with this mix.

What is epoxy casting resin

My skin is irritated from epoxy. Does it do any harm?

Most people have no problems when skin comes in contact with epoxy, but it can occur that an allergic reaction arises. This has no further consequences but is annoying.

When health problems do occur, please consult a doctor. Therefore always use face and skin protection.

What is the difference between epoxy and polyester?

- Epoxy is watertight, polyester isn't
- Epoxy shrinks a lot less than polyester
- Epoxy sticks to almost anything, polyester usually needs a pretreatment
- The chemical persistence of epoxy is in general much bigger than of polyester
- Epoxy smells a lot less than polyester
- The UV persistence of epoxy is less than polyester
- Epoxy is more expensive than polyester

How can I apply best more layers of epoxy?

The most efficient way is to work "wet in wet". In this way you don't have to sand and decrease between the layers.

The next layer is being applied when the former layer isn't sticky anymore but still soft. You should still see a fingerprint. This demands some planning but safes time.

Why doesn't my epoxy cure?

There is a big chance that you didn't use the right mixture (or maybe didn't mix at all?). Too little hardener results in not curing at all. The epoxy doesn't get hard.

Too much hardener doesn't cure the epoxy faster but provides a weaker result.

When you use epoxy at temperatures below 21 degrees Celsius, curing time can be longer. A big surface that is treated at a temperature of 15 degrees Celsius can take upto 1 or 2 days to cure. You can speed up the process by adding for example heat (stove or hair dryer).

What do I use fillers for?

Epoxy is rather fluid and therefore runs throught the cracks. To make a thicker mass, fillers are being added. This can be saw dust, cotton or chopped glass strands.

There are also "high tech" fillers like stewathix, aerosil, and microballoons. These fillers provide a diehard result after curing and are super light whereby the weight stays low.

Can epoxy be put in the garbage can?

Non cured epoxy is a chemical product and should therefore be taken to the chemical waste.

Can I paint/varnish over epoxy?

Ja. That is recommendable. Epoxy is reasonably resistant to UV light but remains better when treated with a UV resistant (boat)varnish. This doesn't necessary have to be a 2-components paint system.

Mr.Boat casting/photo epoxy is UV resistant.

Can I spray Mr.Boat epoxy?

No, our epoxy is not suited for spraying.

It is freezing outside. Can I work with epoxy?

Don't. The ideal temperature to work with epoxy is around 18 degrees Celsius. At lower temperatures upto 10 degrees Celsius you can work barely with epoxy but cure time is much longer then. Besides that it's no fun to work in the freezing cold...

Is epoxy suited for (kite)surfboards?

Yes, and for canoes, caravans, modelling etc. (Kite)surfers often use foam core and that works excellently with Mr.Boat epoxy.

Can I use epoxy on steel of aluminum?

When pretreated well, epoxy can be used well on steel in order to putty for example.

For smaller repairs we sell double seringes with 25ml epoxy which can be mixed with steel or titanium.

How can I apply epoxy best?

With a disposable brush or roller. Redundant epoxy can be removed with a squeegee (rubber spatula). Don't use expensive tools because after curing you can throw it away. Wrapped in aluminum foil, put in the freezer, no curing will take place. But do not place the tools next to your steak for tonight.

With a steel or teflon roller you can press any air bubbles out of the laminate. The squeegee works well for this too.

How long can I preserve epoxy?

Epoxy is tenable for at least 1 year, but in practice more than 2 years. Epoxy can crystalize and become white when temperatures change (cold). Put the can in the sink with warm water for a while and the resin can be used properly again.

How much epoxy do I mix at a time?

Dependant on what you want to do, but not more than you can process in 30 minutes.

If you mix little quantities (less than 100 grams), resin and hardener should be weighed on a (kitchen) scale. Above 100 grams you can mix on volume in the mixing cup.

Can I use resin without hardener?

NO. Only by mixing the resin and hardener, a chemical reaction arises which we need. Resin and hardener are never used seperately but always in combination of the two.

Epoxy for aquarium and terraria

Mr.Boat epoxy is well known among lovers of tanks, terraria and palludaria. It is suitable to glue and coat (usually wooden) boxes, make boxes and back walls watertight and maintenance-free.

Mr.Boat epoxy is after curing completely safe for man, animals and plants.

There is a lot of information available on the internet, especially on different forums. Check for example, or

Why does epoxy gets hot during curing?

The chemical reaction that arises is exothermic. That means that heat is released during curing. That is the result of the reaction which makes a cross connection between molecules of the resin and hardener.

A big quantity in a mixing cup can even start to smoke because of the developed heat. Try to avoid this.

Can you repair polyester with epoxy?

Epoxy is excellently suited to repair polyester.

Is epoxy UV resistant?

The standard Mr.Boat Epoxy is reasonably resistant to UV light and remains better when treated with a UV resistant (boat)varnish. This also applies to most laminating epoxy. If this isn't done, yellowing will occur after some years and a chance on tiny cracks.

Adding epoxy pigments (colour) also contributes to a better UV resistance.

Mr.Boat cast/photo epoxy is UV resistant.

How do I measure resin and hardener?

The easiest way is by mixing in a mixing cup. This is included with all our epoxy and can be used more than once.

Epoxy should officially be weighed. Because of the density of Mr.Boat epoxy you can also measure in volume by using the mixing cup when measured more than 100 grams. When less than 100 grams is needed, use a (kitchen)scale.

Make sure to mix resin and hardener very well. Don't forget the edges. Better to stir longer than too short.

If you don't have a mixing cup, it is easy to make a mixing cup yourself:

Use transparant plastic cups. Fill one of the cups with water, 3 cm. of 5 cm., it doesn't matter. Mark the water level on the cup and mark "H" for hardener. This is the cup for hardener. Take another cup and fill this one twice the amount of the other cup. Mark that water level with "R" for resin. That is the resin cup. Dry both cups before using. Epoxy doesn't like to be mixed with water.

Don't mix the epoxy in foam cups. During curing the epoxy turns hot and the cups could melt! Also do not use glass jars. These can burst through the released heat.

Does epoxy smell?

Non or barely. Unlike for example polyester no gas (styrene) is released with a nasty smell.

What do I use (glass)fabrics for?

Glass fabrics are used to make construction reinforcements. In combination with epoxy a wooden boat can be made much stronger and stiffer. Corner joints can be reinforced with glass tape (strips glass fabrics).

With fabrics you can make form pieces in a mold.

Glass fabrics are available in different weights. The lightest fabric we sell is 25 gram/m2. This is a very fine fabric which is used for modelling for example or model airplane builders. Our heaviest fabric is a 450 grams biaxial glass fabric that is used for heavy duty applications.

Furthermore glass fabrics can be woven in different ways. There is a difference between vierkant woven and keper woven where the last has an angled weft thread. In general keper fabric is easier to fold. But this only applies to somewhat heavier weights.

Besides glass fabrics there are other fabrics with different qualities. For example carbon fabrics (light) or aramid fabrics (also known as Kevlar; resistant to point load). A combination of both is also possible.

Mr.Boat also sells different types of design fabrics for decorative use.

Is epoxy dangerous?

Epoxy is relatively safe. However it is important to take into account some safety measures. Wear goggles and gloves. Epoxy should be stored safely and kept out of reach for children.

Cured epoxy is completely harmless for man, animals and plants.

Do I have to use a prime before painting/varnishing over epoxy?

In most cases it is not necessary to use a primer before using a paint system over the epoxy. However there are paint systems that do need a primer. Always follow the instructions of the manufacturer.

Zelfetsende? primers work reasonably because of the high resistance against chemicals.

What is laminating?

Laminating is impregnating glass fabrics with epoxy. That way a very strong "hull" is being formed after curing around wood for example.

With 1.5 kg. epoxy you can laminate about 4-6 m2 glass fabrics, dependant on the used weight.

The total weight and resin absorbtion of the laminate can be found at the details of the different kinds of glass fabrics.

What does pot life mean?

Pot life is the time mixed epoxy stays fluid and workable. With Mr.Boat epoxy pot life is about 30-40 minutes (at about 20 degrees Celsius). After that the epoxy hardens. Therefore don't make more than you can process in 30 minutes.

You can extend the pot life too by pouring the mixed epoxy into a paint tray with a bigger surface.

What is coating?

To protect wood (or other materials) against external influences, a layer of epoxy is applied with a roller or brush. Don't forget the head end of the wood.

With 1.5 kg. epoxy you can coat about 6-7 m2.

How much epoxy do I need?

It depends on what you want to do. When coating use is about 1.5 kg. epoxy for 1 layer of 6 m2.

When laminating you use more, depending on the glass fabric weight. Heavier fabrics absorb more epoxy than light fabrics. Check out the details of the specific fabrics to get more information about the use of epoxy and laminate thickness.

What is a fillet?

Een fillet is a (epoxy glue) connection between wood parts with thickened epoxy. This thickening takes place by adding fillers to obtain a thicker paste. The ideal thickness looks like pinut butter. Then a "caterpillar" epoxy is applied to the parts to be glued. These are wiped away half round with a tongue depressor.

You can apply the "epoxy caterpillar" easily by putting the thickened epoxy in a plastic bag where you cut off the point. This way you have a cheap pastry bag.

Apply a thin layer of epoxy on the surface to be treated before making the fillet.

Suitable fillers for making epox glue or fillets are aerosil, stewathix or cotton.

Connections with epoxy fillets are even stronger than the individual parts.

What colour has epoxy?

Mr.Boat epoxy is transparant with a light yellow shadow. When applied on glass fabric this also becomes transparant. Any wood grain on the underlay remains visible.

Mr.Boat casting/photo epoxy is crystal clear.

How do I make an epoxy glue?

Epoxy glue is made by adding a filler to the epoxy to make it thicker. Thicken the epoxy untill the mass looks like ketchup. Apply to the parts to be glued and press lightly. Epoxy needs space to suture well. This unlike traditional wood glue which needs long heavy pressure in order to suture.

Suitable fillers for making epoxy glue of fillets are: aerosil, stewathix or cotton.

Can I colour epoxy?

Yes that is possible. Use the special colour pigments. Add a little bit (about 1-2%). Provides a transparant colouring. When adding more, the result is a "piano varnish" effect.

Adding pigment also means that UV resistance will be improved.

What is the mixture?

For Mr.Boat epoxy and Mr.Boat injection epoxy: 2 parts of resin and 1 part of hardener. Thus 2:1.

For Mr.Boat casting/photo epoxy there is a mixture of 1:1.

How do I make epoxy putty?

Epoxy putty can be made easily yourself. Choose a filler, for example microballoons and mix this with epoxy untill the desired thickness. Voila. Epoxy putty at a low cost.

Apply a thin layer of epoxy on the underlay before applying epoxy putty in order to improve the suture.

Don't feel like mixing yourself? We also sell handy ready to go epoxy putty in 400 and 1000 grams packagings.

Gelcoat repair with epoxy

Epoxy is excellently suitable to repair damage in the gelcoat. Epoxy is stronger than gelcoat and doesn't shrink.

Roadmap for small damage to the gelcoat
1. Mill the damage with a Dremel met bolkopfreesje. No loose parts should be left and make sure to mill the edges slanting upto the undamaged gelcoat. Try to leave the underlying polyester with glass fabric undamaged.

2. Sand the edges with a fine grain untill they are nice and smooth.

3. Clean the repairing part and make it dust free with acetone. Acetone also expels any present moist. Watch out: acetone is flammable and dissolves alsmost anything (except polyester). Wear suitable protection.

4. Tape the rapairing part tightly so that epoxy only covers the part to be repaired.

5. Mix some epoxy putty first and add small amounts of pigment (colour) untill you have the right colour. Preferrably a little less than too much. You can always make it darker, not lighter.

6. Spread the repairing part as tight as possible with the coloured epoxy putty. Use a putty knife or squeegee.

7. Remove the tape and let it cure (cure time dependant on the surrounding temperature).

8. Sand smooth with an even finer grain. Next the spot can be polished or, if the colour isn't quite right, you can use a paint system as finish.
This can be a 1-component or 2-components paint (or UV resistant varnish).

Above roadmap is meant for small repairs, cracks and stars. Other technics are required to repair bigger damage or holes.

What is MS Polymer?

TEC7 is a super product. It replaces mounting glue, wood glue, PU glue, silicone kit, sanitary kit, acrylic kit and butylene kit. TEC7 kit is used for indoor and outdoor and provides a super strong, elastic result which can be painted right away.

Almost all materials can be glued with TEC7; metals, synthetic materials like: PVC, polyester and perspex, brick, concrete, cork, glass and most woord types.

Tec7 becomes even hard under water, is very water(sea)tight and doesn't release any toxic substances.

For example a breach in an aquarium can be repaired under water.

What is peelply?

Peelply of tear fabric is a fine fabric treated with nylon. It is applied as first or last layer on the epoxy laminate. After curing of the laminate the peelply is stripped under an sharp angle. This leaves a waffle type of structure which you can immediately use for further treatment without having to sand of decrease.

Peelply can also be used to prevent amine blush.

Available in 15 and 100 cm. width.


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