Firstly, I am sorry you had a problem with our product. The material is made in batches of 2000 litres and each one is checked for setting time and final cure and adjusted with chemical additions to get the right Gel Time and cure before packing off. It is not possible to have a “bad can” that is outside specifications and, as it ages over a period of 5 to 10 years, the gel time and cure time get shorter until the shelf life is used up and the stuff is then hard in the can.

Therefore there are 3 ways the material can fail to set: insufficient hardener; too much hardener; or a chemical in the timber (such as metalex preservative, or some epoxies) which inhibits polyester cure. The latter will only spoil the bond to the timber but the bulk of Builders Bog will still cure OK. The smell you now have will be unreacted styrene, which is the cross-linking agent in our formula, and should all be used up by chemical reaction if proper cure took place.

The only way to remove the smell barring waiting a long time for it to evaporate, which could take months or years, is to scrape it out and re do it using the correct amount of hardener as specified. If I were you, to satisfy myself, I would cure a small amount after careful measurement of the two components – and remember we give a huge permissible operating range for the ratio in the instructions – and observe that it set fully in about 20 minutes on a piece of scrap.

Setting time depends on temperature, of course, and the thickness of the repair. A thicker repair generates much more chemical heat (up to 80 deg. C or more) and will therefore cure faster and have a shorter “spreadable” and “cheese-grateable” time. You can also judge by colour and should see something like the pictures attached, depending on the colour settings of your monitor, of course. I hope this helps and again sympathise with your problem.

I suspect you may have insufficient hardener in the mix, because on a bigger job one has either to work very fast or apply multiple layers. The gel time is set at 6 to 9 minutes at 22 deg. C so that a tradesman can complete a job, sand it and paint it in the same half day, unlike solvent based fillers which necessitate repeated visits on successive days due to the long drying times involved. The temptation is therefore to use less hardener to prolong the working time, and move outside the minimum ratio permissible for proper cure. Please feel free to contact me again if you have further worries or questions.

Regards
Stuart Jordan
Managing Director