West System 105 Epoxy Resin 1Kg (105-A)

West Systems

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Part Number: MIWS105A
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Due to the current "LOCKDOWN" situation imposed tonight 23rd March 2020 at 20:30, we are experiencing delays with the processing of orders and subsequent shipping.

Whilst we have tried our best to continue in a business as usual, the time has come when we must close our showroom doors temporarily to support the Governments Delay Strategy.

If you do place an order with us, we will be shipping items from our warehouses, but it may be subject to a delay.

Should you wish to speak to a member of our team, please call us on 02087884587 and Choose Option 1. Alternatively, please email shop@chasnewensmarine.co.uk

105 Epoxy Resin

105 Epoxy Resin is the base material on which all WEST SYSTEM 105 System epoxy compounds are built. It is a clear, pale yellow, low-viscosity liquid epoxy resin. Blended with hardener at the proper ratio, it cures to a hard, solid plastic with superior physical properties. Based on which hardener you choose, it cures at a wide range of temperatures.  Once cured, it forms a high-strength solid that is functionally waterproof, and highly resistant to moisture vapor.

We designed 105 Epoxy Resin to wet out and bond with wood fiber, fiberglass, and reinforcing fabrics. It also bonds well with a variety of metals.

Epoxy vs. Esters

We’ve formulated 105 Epoxy Resin (and its corresponding hardeners) without volatile solvents. Unlike polyester or vinylester resins, our epoxy virtually does not shrink after curing. With a relatively high flash point and no solvent odor, it’s safer to use than styrenated resins.

Thickening Epoxy

Modifying this epoxy with WEST SYSTEM fillers creates an excellent structural adhesive or fairing compound. You choose the filler that suits your project. Epoxy thickened with adhesive (high-density) fillers makes structural bonds, bridges gaps, and fills voids. Epoxy thickened with fairing (low-density) fillers is easily sanded and shaped after it cures.


This epoxy is also a great coating material.  Applied with a roller, it offers excellent thin-film characteristics. It will flow out and self-level without “fisheyeing.” By combining it with blush-free 207 Special Clear Hardener, you can create a natural finish. You’ll just need to add a couple of coats of varnish for UV protection. This is a good alternative that builds mil thickness quickly, saving time and effort. The results are long-lasting.

105 Resin’s viscosity is approximately 1000 centipoise (cp) at 72 F (22C).

Pair 105 Epoxy with corresponding letter size of 205 Fast Hardener, 206 Slow Hardener, 209 Extra Slow Hardener or 207 Special Clear Hardener.


More Facts about WEST SYSTEM Epoxy

Using gel coat over WEST SYSTEM 105 Epoxy Resin and Hardener

It’s a myth that if you plan to gel coat over a repair, you must make the repair with polyester. We’ve used gel coat over epoxy for decades. It’s in our fiberglass boat repair videos and discussed it our magazine, Epoxyworks.

There are three key factors for success with gel coat over epoxy:

  1. Mix your epoxy resin and hardener at the proper ratio (Mini Pumps make this a snap).
  2. Allow the epoxy to fully cured.
  3. Before applying gel coat, remove any amine blush from the cured epoxy surface. Amine blush is simply an easily removed wax-like film that can form as a byproduct of the curing process. WEST SYSTEM 105 Resin/207 Special Clear Hardener does not blush.

Gel coat manufacturers shy away from approving the use of non-air inhibited gel coat over epoxy because they’re concerned amine blush will interfere with the gel coat’s cure. All you need to do to remove the blush is wash the surface with plain water. It’s then ready for you to prep for paint or gel coat.

This process is even easier if you use Release fabric. This fabric is applied to uncured epoxy, protecting the surface from contamination. As the epoxy cures, any blush will form on the outside of the release fabric. Simply remove the release fabric after cure, and it will take the blush with it. The resulting surface is ready for you to prepare it for paint or gel coat.

Epoxy’s penetration into wood

Epoxy does more than sit on the surface of the wood. Some epoxy will remain on wood surfaces, and some of it will penetrate into the wood. The amount of penetration depends mostly on how the wood fibers are oriented. Face grain will not absorb nearly as much epoxy as end grain. But since WEST SYSTEM Epoxy is very strong and an excellent adhesive, it strengthens the wood and makes it waterproof.

105 Epoxy Resin batch size and cure speed

You need to know that in larger quantities, epoxy cures much faster. This is because epoxy generates heat as it cures and also cures faster at higher temperatures. This snowball effect increases until the epoxy cures—which in very large batches could take only a couple of minutes. Large pots of mixed epoxy can generate enough heat to cause a runaway exothermic reaction. This can include, smoking, melting the mixing cup or even starting a fire. Spreading epoxy thin allows the heat to dissipate and slows its cure.

Epoxy casting 

WEST SYSTEM Epoxy has a very low percentage of shrinkage. In fact, the standards used to calculate shrinkage of other resins (polyester and vinyl ester) aren’t used with WEST SYSTEM because it shrinks so little to measure that way.

When epoxy is used to fill holes drilled into wood, it will soak into the end grain. This might look like shrinkage, but it’s not.

Back in the late ’70s and early ’80s, Gougeon Brothers Inc. manufactured over 4,000 wind turbine blades and their molds using WEST SYSTEM Epoxy. It was commonplace to see a 70-foot long mold shrink 3/32″ over the entire 70-foot length. That represents shrinkage of just .01% on a laminate consisting of fiberglass and WEST SYSTEM Epoxy.

Avoiding exotherm when casting

When casting epoxy, heat buildup can become an issue. Excessive heat can make WEST SYSTEM Epoxy can shrink some. Pouring epoxy in great depths creates the potential for the epoxy to get very hot due to the exothermic reaction resin and hardener have. While exotherm is a normal part of the curing process, you must always keep it under control. Do this by using smaller pours when casting, and working in a cool environment.

Any shrinkage that does occur generally happens while the epoxy is still liquid, but when an intense amount of heat is present, epoxy doesn’t stay liquid for very long. As the heat dissipates, the difference in temperature between the top and bottom of the casting can shock the now solid epoxy and it may crack. To avoid this, make deep castings in layers.

Adding extra hardener (don’t)

While adding extra catalyst to polyester resins can lead to a faster cure, you should never add extra hardener to epoxy resin. Epoxy reaches cure when the resin molecules cross-link with hardener molecules. When there is too much of either resin or hardener, unlinked molecules are left over. This can result in uncured epoxy or compromised cure strength. Always mix epoxy resin and hardener as close as you can to the recommended ratio.

Clamping force

Unlike traditional wood glues, WEST SYSTEM Epoxy is stronger than wood. Because of this, it is beneficial to have some epoxy between the objects you are gluing together whether they are wood, fiberglass, or other materials. As long as the epoxy is contacting the entire surface of both substrates, no clamping pressure is needed.

The goal clamping is to simply ensure the epoxy contacts the entire surface for the duration of the cure time. Moderating clamp force is all you need. If you aren’t using a filler, and apply too much clamping force, this can result in a glue-starved joint. This makes future joint failure much more likely. Glue starved joints are weaker than their counterparts. Avoid glue-starved joints by following the one- or two-step bonding method.

Filler and Epoxy Strength

While certain fillers will increase the density of epoxy, this does not correlate to higher physical properties or increased adhesion strength. Epoxy is strongest without filler added to it, but the fillers are necessary to:

  • Increase the viscosity of the mix
  • Bridge gaps
  • Prevent the epoxy from soaking too far into the wood
  • Prevent glue-starved joints

Epoxy and Rotted Wood

Rot eats away the cellulose fiber in wood. Cellulose is the structure of the wood. Replacing it is not as simple as brushing on a coat of solvent-thinned epoxy. Solvented epoxy may replace some of the strength, but isn’t a permanent repair—it won’t restore the strength of the wood fibers. To make a permanent repair, replace the entire rotten area with fresh wood and sealed with epoxy. Addressing rot this way will make the repair area stronger than it was before the rot occurred.

Why remove rot?

Rot needs four major components in order to continue growing:

  1. Food
  2. Moisture
  3. Oxygen
  4. Warmth

Cutting off just one of these components is enough to cause the rot to go dormant. Solvented epoxies are supposed to cut off rot’s food source by encapsulating and contaminating the wood that the rot spores consume. However, the remaining three components: moisture, oxygen, and warmth, can still penetrate wood coated with solvented epoxy.

This is because solvented epoxy is a poor moisture barrier. Rot spores will remain in the wood, and even when encapsulated in solvented epoxy, they will only go dormant. Un-isolated rot pores will continue devouring the cellulose, causing more rot.

This is why we recommend removing the rotten wood and replacing it with fresh wood that is sealed with several coats of WEST SYSTEM Epoxy.

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West epoxy system is excellent!

Please see below our shipping rates, while we endeavour to keep them correct, may from time to time, they may come up too expensive on smaller items, in this case, please contact us and we will try and find a more competitive rate for you.

Priority Shipping - Mainland GB Only
Economy Shipping  - Mainland GB Only
Highlands and Islands Economy Service - 2kg to 5kg
Highlands and Islands Economy Service - 5kg to 10kg
Highlands and Islands Economy Service - 10kg to 20kg
Oversize Parcels will require a specific shipping quote. 

We also offer calculated shipping Worldwide using UPS. For more information, please follow the checkout process with your selected items.


Last Updated: 20/03/2020

Our returns policy lasts 30 days. If 30 days have gone by since your purchase, unfortunately we can’t offer you a refund or exchange.

To be eligible for a return, your item must be unused and in the same condition that you received it. It must also be in the original packaging.

To complete your return, we require a receipt or proof of purchase.

Please do not send your purchase back to the manufacturer.

To read our full returns and exchanges policy, please click here.


Some items we sell may from time to time be subject to Age Restrictions imposed under UK Law. 

Where this affects your purchase, you will be contacted by a member of our sales team, you will be required to provide us with a copy of photographic identification, from the list below.  A valid photographic ID will also need to be shown to the driver on delivery, along with a signature.

By sharing your ID, you are helping us to ensure items that are intended for people over 18 end up in the right hands. Due to the importance of verifying age when delivering these products, age restricted items can only be delivered to the customer’s address, they cannot be delivered to a neighbour’s address or left in a safe place. In addition, they can’t be delivered to a locker or Pickup Point.

If an adult over the age 18 is not available at the address, or if an adult has not been able to show valid photo identification, the item will be returned by our couriers for re-delivery the following day. If your order is being delivered to a commercial address or residential apartment block, the receptionist, concierge or mailroom attendant receiving your parcel will need to provide a valid ID, showing they are aged 18 or over.

If they can’t, the parcel will be returned to our couriers for re-delivery the following day.

List of acceptable photo identification:

  • A passport
  • A European Union (photo card) driving licence
  • Ministry of Defence Form 90 (a defence identity card issued to serving military)
  • National Identity card issued by European Union Member State (other than the United Kingdom), and Norway, Iceland, Liechtenstein or Switzerland
  • A biometric immigration document (issued by The Home Office to individuals going through different stages of the immigration process as a residence permit.).
  • A photographic identity card bearing a national Proof of Age Standard Scheme (PASS) hologram

All information we receive about customers is treated in accordance with our Privacy Notice, which can be found on our website.

Thank you for your understanding as we do our part in ensuring compliance with UK Law.

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