West System 205 vs 206

Hello, I recently ordered my 1st kit, a Chesapeake 17 and it is currently in route to me in Alaska.  However, due to shipping restrictions the MAS epoxy system was not able to be bundled with my kit, I'm on my own to get my epoxy.  Locally, only the West System is available in the realistic quantities I need for my project.  As I'm collecting my materials I'm curious if anyone can offer me some advice between selecting the 205 or 206 hardener?

I know that the 205 is the fast and 206 is the slow so as a novice I'd initially think the 206 would be more my style.  However, when I look at the working temperatures I see that the fast hardener has a lower working temperature than the slow hardener.  In fact, the slow (206) doesn't seem to show a working range much below 60degrees.  My unheated garage will be my workshop for my winter project and while it does stay above freezing because of the mechanical and space heaters I put in there I'd most likely be working in 40 to 60 degrees for the duration of the project.  

So with that said, would the fast hardener (205) be a better choice?  It looks like its range goes as low as 40 degrees.  Also, I'd assume that working at those lower temperatures I'd get more working time as well?  Of course this is all info I'm interpreting by looking online so I'd appreciate any firsthand knowledge.

9 replies:

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RE: West System 205 vs 206

Hi jetescamilla,

you are going to be working at the edge of things...working in the winter takes some thinking and some experimentation.

so the first thing i would like to suggest is that you keep your epoxy heated (by keeping it inside or using a local heat lamp) so that it stays in the high 70's low 80's.  cold epoxy is difficult to mix at low temperatures.

once its mixed, you can apply it to lower temperature wood.....but you will need to have enough temperature for it to cure.....but it won't cure well if it is not mixed well.

based on my experience, which also included winter work where it was challenging to get my garage above 60, i like having more time and would go with the slower.   the other thing i do in the winter is use plastic tarps with my space heater so i can keep the hull warm and not be heating the whole garage.  so between the pot life of pre-heated epoxy and getting the epoxy on the wood in the winter, i have not had an issue.  the key pieces has been the plastic tarp and space heater to heat the wood/epoxy after it is all applied to actually allow the epoxy to cure.  its a bit of a process but it did work for me...albeit much slower than working during the summer.

every boat build is a bit of an experiment.....


RE: West System 205 vs 206

Yes to what h said above, and double yes to the fast hardener (205), having looked at the West System info here:


If you can't keep your work area above 60 degrees, you'll likely be waiting a lot for the 206 to cure, and you'll be tempted to push things.  If the temp is much below that, it might not cure at all.

When be built our Passagemaker Dinghy in our unheated (and uncooled) garage here in Central Ohio, we did most of the work over the summer.  The MAS slow hardener supplied with the kit worked well for us, and we were able to keep the work moving along without having to wait very much for epoxy to cure.

Once we got into mid-September and October, we were glad that we'd gotten most of the work finished when it was warmer, as the cure times began to stretch out to the point where we had to resort to space heaters, 100 watt incandescent light bulbs (remember those?) arranged under or over the boat, and other such tricks to get the project completed in November.  Otherwise, we'd have had to switch to the fast hardener or suspend the work until things warmed up in the spring.

Unless, of course, you can find a big, ol' pot bellied stove and a nice pile of anthracite coal to keep your Chesapeake 17 warm and cozy while she incubates....  <;-)

We wish you all joy of dodging the ice floes in your well cured kayak!


RE: West System 205 vs 206

   Thanks for the responses!  I was fairly certain I was on the right track.  As a structural engineer I read spec and data sheets pretty good but I don't have the first hand insight into fiberglassing a boat (although I will soon).  My plan would be to keep the epoxy containers in my mud room on the radian floor tile to keep warm prior to my application day this way it'll stay nice and viscous.  I'll definitely use some of the techniques mentioned above with the tarping and warming to ensure the epoxy sets correct.

Late last night I found West System has an indpeth "Cold Temperature Bonding" page specifically for my initial posted question.  It's linked below if anyone is up to reading, however a lot of it is repeated by the good practices that were mentioned with the above posts.


Thanks again!



RE: West System 205 vs 206

Jesse good luck and good boating with your Chesapeake 17 once you get it built & launched!

A brief caveat about using WEST System epoxy: read up on amine blush & how to avoid problems brought about by its presence. Low temps during use and cure where relativerly high humidity in the build environment is present will likely as not lead to its appearance.

It can't be sanded off, in fact sanding without a thorough water-wipe & dry first will only serve to drive it into the surface texture sanding creates.

Blush is water-soluable and not much water is needed. Simply using damp cloths to wipe down cured WEST epoxy is enough to remove it when done with care.

Some builders (myself included) advocate using water-dampened ScotchBrite or similar non-woven abrasives (Norton's is a product I use) instead of cloth. The abrasive's effect removes the smooth, glossy surface as well as making the blush removal process more efficient for the time spent. Followed by a damp cloth wipe, once dry the surface left behind is better able to bond propely to additional epoxy or finishing products like varnish or paints.

RE: West System 205 vs 206

spclark, thank you for that invaluable info!  At this point (waiting for my kit to be delivered tomorrow) I think I've talked myself into going to Home Depot tomorrow and purchasing a garage heater just to ensure I don't have to complicated tenting or worrying about blush building up from cooler temp curing.  I'm not looking to get my garage to 80 but if I can keep it at 60* then I imagine a lot of the headache goes away.  Seems it would be well worth the $200 heater I've just looked at online.


RE: West System 205 vs 206

60°F is a good aimpoint for ambient temp epoxy cure, 65°F's even better. Warmer conditions will help when applying epoxy, why it's helpful to put a heater or even heat lamps under a work-in-progress so the epoxy's applied to a surface that'll not only keep it warm and fluid during placement but also help with limiting outgassing during the cure stage.

Outgassing happens when raw wood and plywood are coated with epoxy then subjected to warming temperature. Gasses in the wood/ply expand into the epoxy to cause bubbles. Applying epoxy to pre-warmed wood/ply mitigates this to a great degree if the project material is allowed to cool slowly during curing, keeping gas emissions to a minimum. Prolonged cure times because of low temperature give blush more time to form.

Even still it's advisable to be aware of blush formation with WEST products. Blush can form under even optimal cure conditions. It's not difficult to remove as long as it's done at the proper time. It WILL give you a real PITA for future epoxy bonding if not removed. That link I provided above explains what's necessary but if you want to read more, point your browser-of-choice at this link for even more info.

RE: West System 205 vs 206

WEST touts their 207 Special Clear Hardener as being blush-free if that helps you any.

60*F is the minimum cure temp they recommend, working 'pot' life of 20-22 minutes @ 72°F, full cure in (likely) 7 days @ 60°F.

(There's no escaping the time + temperature nature of epoxy chemistry with the products that are commonly used for projects such as ours.)

207 carries a premium price for its blush-free character, nearly twice what their 205 & 206 hardeners cost.

RE: West System 205 vs 206

   This thrad caught my eye, had same proble running short on epoxy but was using MAS form CLC. There's a West marine close by so rookie question; can i use MAS resin with WEST hardner? assume not, since MAS is a 2:1 vs 3:1 and 5:1 for WEST systems....

RE: West System 205 vs 206

No, don't. You'll rergret it if you do.

Chemistry's different between products, they're not compatible with one another or somebody, somewhere would have posted that it's fine to do so by now.

Sometimes within brands you can use a particular hardener with a different resin or vice versa. MAS LV uses the same hardeners as their FLAG resin for instance. 

With WEST System their 105 Resin product has three different hardeners that will work.

With their G-Flex toughened epoxies (650 & 655) you can use them straight, or if desired for a specific purpose, mix them with their 105 resin & hardener products.

BUT you need to mix G-Flex resin + hardener together first, then mix a measure of 105 resin + one of the three hardeners first, (using the proper proprtions for each combination) then mix the two resin+hardener combinations together before applying to your workpiece.

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