MAS Epoxies, differences between Epoxies, Vinylesters and Polyesters?

Epoxies, Vinylesters and Polyesters represent two resin familes. Epoxies can be cured with amine agents at room temperature to form excellent adhesive and composite resins. Vinylesters and Polyesters contain an unsaturated ployester or hybridized vinylester backbone which is catalyzed with a peroxide to condense into cross-linked solid resin. Read more about Epoxies, Vinylesters and Polyesters…

Natures Head, How do we remove buildup in the liquids bottle.

Rinse the bottle, add vinegar and some pea gravel. Shake well and the buildup will break loose.

MAS Epoxies, Glassing with Knitted Reinforcements?

Knitted reinforcements (as opposed to woven rovings and cloth) come in a variety of weights (usually described in ounces per square yard or gram’s per meter), fiber orientations, and with various backings stitched onto the reinforcing fibers with bias yarn

What is a blistering

To understand the repairing of blisters, we should first understand the cause, Polyester Resin is used in the production of most boats now afloat and it’s not waterproof. Polyester Resin has a very high osmotic absorption rate (how much water the solid absorbs). Usually, water penetrates the gel coat below the water line; however we’ve seen instances where blisters appear above the water line as well.

Blisters are caused when the water passes through the outer skin of the laminate, i.e. Gel coat .When migrating water finds an osmotic home and begins to collect, pop, you have a blister. A blister is an area within the glass that expands to hold more water and causes the laminate to swell. Blisters may show as a bulge on the surface. This can look like a pea or a grapefruit under the skin. When this happens, the laminate begins to soften and the boat can gain substantial weight by absorbing water. Blistering can be prevented by barrier coating a hull with carefully chosen osmotic barriers, like epoxies.

Osmosis treatment and protection

take off the gel coat grind back to a solid substrate wash the area down get rid of all dirt and salt take off all underwater fittings (osmosis will have gone under these) now dry the boat out cover the whole boat with a cover leave both ends open and let the air dry the hull (if you have a shed this time will be greatly reduced) spot repair any holes etc build up with cloth any areas that have shown signs of stress around fittings feels rudder supports etc then two sealing coats of low vis resin and slow or medium hardener followed by 5 coats of flag and slow or medium hardener allow to cure. cut back when sand-able apply desired anti fouling when cured (Mas has one of the highest stretch factors in marine epoxy 8% which will still let the ship work)


Barrier coating will prevent blistering when you use the right product. Check with the manufacturer of the barrier coat product you intend to use. The two question you want answered before using any product are

1.What is the osmotic absorption rate of the product?(How much water it will allow in)
2.What is the bond (secondary) strength? (Will it stick to the surface you’re coating?

Don’t be surprised, when you call. If barrier coat manufacturers may not have this information available. Also be cautious of claims which state Vinyl ester products out-perform epoxies. Since Vinyl ester is a esterified epoxy hybrid it’s unlikely it will out perform a 100% solid epoxy.

Mas Epoxy is comprised of 100% solids and its water absorption is less than 0.5%- the lowest osmotic absorption we’re aware of, and its secondary bond strength is 1850 p.s.i.- the highest available.


To begin, you’ll need to remove all paint on the surface and have a clear view of where the blisters are. Once you’ve located the bubbles or blister on the surface, on the larger blisters, you’ll need to drill a hole in the lower portion of the blister to allow the trapped water, etc. To escape. After this is completed, you’ll need to grind away the complete blister – like an upside down volcano into the laminate is ground away when you hit hard, clean material again.

We should mention the water behind the outer skin will smell and the material will be spongy in texture and discoloured.


Feather out the edges of the divot you’ve created. A feathering ration of at least 8:1 will allow permanent secondary bonding of the repaired area. When you’ve completed the removal of all blisters, allow the boat to dry by storing in doors or tenting the hull from the whether. You may also consider applying heat to help dry out the composite before you begin to repair. Get hold of a moisture meter and check the moisture content of the hull. If you can’t get hold of a moisture meter, please call us for recommended dry schedules.
Now you can begin rebuilding the surface. Our recommendation for filling back divots making your own filler by blending Phenolic Micro Balloons (Purple in colour) and Colloidal Silica 75/25 respectively. (See Fairing recipe on page 21.)

Now fill back the holes using a putty knife or large squeegee. If substantial structural glass has been removed in the grinding process, new glass can be applied prior to applying filled epoxy or Fairing Compound. Let the epoxy filler mix harden for 12-24 hours at 77 degree f before attempting to sand or work the surface. Depending on the temperatures, you’ll have to check the surface for hardness before you continue working. To re-coat, use the ” Rule of Thumb”- If you can leave a thumbnail dent in the surface, and there’s no amine blush, then you can repeat without the 12-24 hour window. In cooler temps., 35-65 degree f, if it’s still soft, throw some heat at it or be patient, it will cure.

MAS Epoxies, what is the Mix Ratio?

Generally the mix ratio is 2:1 Resin to Hardener. That ratio stays the same when the hardeners are custom blended (See item 19). When blending hardeners, blend In separate containers from the resin then mix with the Resin. Be sure to maintain the 2:1 ratio, resin: hardener.

However this changes to 5 parts resin to 1 part hardener if you use our traditional Boat building epoxy if you have any concerns contact us on 07904446306

  • MAS Epoxies, Cure Schedules
  • MAS Epoxies, blister repair and barrier coating

To understand the repair of blisters, you should learn what causes them, and before you apply a barrier coat on a new surface,

MAS Epoxies, will extra hardener help

Can I speed up the mix my adding more Hardener – ABSOLUTELY NOT! Adding more hardener throws off the ratio and you will end up with a gooey mess that never cures.

MAS Epoxies, how much mixing is required?

Mixing is the key to a thorough cure, good films and strong bonds. One and a half to two minutes of aggressive mixing, swiping the sides and bottom is recommended. Be sure mix ratio is two parts resin to one part hardener. (2: 1). Use clean plastic or uncoated paper cups or buckets and a clean mix stick.

We also recommend taking the mixed batch and putting it into a clean container, scraping the sides and bottom and then mix again. this assures a complete mix.

MAS Epoxies, what is BLUSH/WAX, how do I remove it?

Blush or Wax is noticeable as a slippery film formed over the cured surfaces. It can be removed with warm water and a sponge (rinse and wipe). All the current MAS Hardeners used in a 2-2-1 mix ratio are Non-Blushing, No wax formula.

If you use other products that do produce wax or blush you must remove the wax blush with warm water (some say with soap, and some diluted acid. Do yourself a big favour move away from these they are pure aggravation , Join the MAS Family remember simple perfection why make life hard

MAS Epoxies, What is the recoat time?

Since epoxies from MAS are 100% solid (no solvents), recoat time can be as short as it takes to achieve surface tack. If more than 12 hours passes between coats, do a light scuff sand. Use a cotton ball to test if a light scuff sand is needed. If the epoxy holds the hair of the cotton ball, you can recoat without sanding. If it doesn’t, a light scuff sand will help adhesion between coats. Remember the “Rule of Thumb” test (if you can press your thumbprint in the epoxy, but there’s no tack, then you should do a scuff sand, but will be getting a chemical as well as a mechanical bond.) Remember, warmer conditions makes for a faster

MAS Epoxies, temperature requirements?

For clear coating, we like to see the resin remain over 55 to 60 F. For bonding, anything over 45 F is adequate.

The above is information from the factory , we have had good results at temperatures a-lot lower than this but we have warmed the resin first and used a medium or fast hardener in really cold conditions a heat gun can also be used

99% of the time the epoxy will go off and cure however the colder it is the longer it takes, mid winter epoxy work gets done with warm epoxy then we wrape everything up and put a small heater on the project as long as there is some heat to start the cure you will be fine

MAS Epoxies, how to clean up?

Gloves and other personal protection should always be used. If you should get any epoxy on your skin, it should be cleaned off with a waterless soap immediately, then thoroughly washed with soap and water. Tools can be washed with Bio Solv, white vinegar or isopropyl alcohol. Semi-gelled epoxy can be removed with acetone. (do not allow acetone near your work)

MAS Epoxies, What tools are used to apply the epoxy?

For coating and fiberglass, a short nap 1/8″ nylon bristle roller, plastic squeegee, or disposable brushes. For bonding, a glue brush or a squeegee with notches cut into the edge.

MAS Epoxies, how to protect the epoxy?

Epoxy surfaces should be protected from sun exposure. Clear coats may be protected by a good quality varnish or urethane with UVA protection additives. Paint is always considered a 100% filter. Indoor pieces do not need varnish over epoxy.