Epoxy resin soft spots

[Lance Reid]

After laying the resin and leaving for a few days, there is a softer patch in the resin.
Will this eventually harden or would it need other work?
Resin is West Systems 105 with 207 hardener

[q9]

Low heat for a while might help kick it along. Incandescent bulbs throwing a very warm, but not hot heat should be enough. Maybe give it a day.

[justonething]

How did you measure the quantities of resins and hardener? Because it is a 1:5 (or 1:4) mix. It is not possible to mix it by eye and get accurate measurements. You either get one of their pumps or use a digital scale. Your not hardening may be due to insufficient hardener.

[Big Shed]

If it is patchy hardening it is more likely to be insufficient mixing of the 2 components.

As said above applying heat to the offending patch may speed up the reaction.

[Lance Reid]

Measured out using a container filled to the same level each time.
Will give it a low heat tomorrow and see what happens, thinking it was more than likely poor mixing.

[Lance Reid]

Ended up removing the soft mix and adding another layer.

[Nanigai]

Good, but don't get tricked into adding a little extra hardner to make it go off better, it's a no no.
By the way don't ask how I know this
cheers, Ian

[q9]

Yep, stick strictly to the mixing ratios provided. Otherwise you'll make an industrial chemist cry...

[Lance Reid]

Good, but don't get tricked into adding a little extra hardner to make it go off better, it's a no no.
By the way don't ask how I know this
cheers, Ian

Had been told that varying the ratios wouldn't be good.

[Wood Collector]

Do you get too much heat if you add more hardener?

[q9]

It ends up being soft as it has nothing to react with. Mechanical properties go out the window when you alter ratios.

[soundman]

For those not familiar with the modern marine epoxies and those related.

IT must be understood that these are epoxies, they are nothing like many other resins people encounter ......... Yeh Yeh I know .... but people just won't be told.

They must be mixed accurately, there is some small leeway, but they must be mixed accurately ...... they are not resin and hardener like other resins, they are part A and part B. .....the word hardener may be used, but it realy is inaccurate particularly in the later generation products ......... there is absolutely no advantage of adding more of one part or another.

In modern 2 part epoxies ( there are single part epoxies), the whole of both parts of the product react and become the reacted, hardened product ....... any surplus of either part is a problem .... very small amounts of unreacted surplus will rise to the surface and not impeed propper setting of the product .... ( this is pretty much normal in every mix of West System) .......

Significant excess of either part will cause the product to either fail to set, not set up hard or fail in the future.

For the same reason it is absolutely imperatave that these modern marine and related epoxies are very well mixed ......... in other two part resins the hardener or catalist is a solvent or is carried in a solvent ...... these hardeners are highly mobile in the mixing container and travel thru the unreacted resin redily on their own. ....... the two parts of epoxies will not mix on their own, they tend to stick to the sides on the mixing container, they require to be actively and thoroughly mixed. ...... you must mix well, systematicly and scrape the sides and the bottom of the container ..... using containers with lumps and bumps on the inside (like soft drink bottles) is illadvised.

Failure to adequately mix will result in parts of the job with excess of one or the other of the parts ...... the result parts of the job that fail to set, fail to set hard or fail in the future.

The more accurately you measure and the better you mix the more reliable the job will be.

One measuring.
I have used suringes, pumps and containers.
I have found pumps unreliable and marginal for accuracy.
For very small amounts of West, I will use suringes........ boat coat however is too thick for suringes.

I find it best to mix in graduated plastic measuring containers ........... the only way to achieve real accuracy is to pour directly into the mixing container ....... you must wait for the part a to settle before you read, then you must be incredibly carefull adding part B ....... let settle and drip drip till it is right.

I reuse the measuring cups over and over ....... when I have scraped out the mix I place the mixing stick in the cup .... when it is off the surplus pulls straight out of the cup leaving it clean for reuse.

YOU MUST be carefull with this stuff ......... you must work is a very well ventilated area ..... I mean fan forced ...... avoid skin contact as much as possible.

Given enough exposure EVERYBODY will develop sensitivity to these epoxies ....... some will react badly from day 1.
West is far worse than Boat Coat for reaction ...... headaches are common ( minor brain damage) some will get a skin reaction from the fumes alone.

A bloke I know .... who would not be told ...... had a red rash on his legs for 3 months because he did not cover up.

Do not clean you hands with solvent ...... it helps the toxins traverse the skin barrier ........ Acid is you friend ....... Citrus industrial hand cleaner is by far the best ........ failing that vinegar or citrus juce and soap will shift uncured epoxy.

Sorry for the long wind ...... but these epoxies are fabulous ...... BUT, they are intolerant of poor practice.

BTW if you want epoxy to go off faster or slower , you use faster or slower part B. ........ the proportions of the mix must remain accurate.

cheers