Friday, 11 July 2014

Relative Humudity

When The Boss sets up the ironing board once a week I usually take it as a sign that it's safe to sneak off to the modelling room for an hour or so of uninterrupted work.

So it was this week when I thought I would grab the chance to get stuck into the mountain of resin casting work I've got building up. (The FR shop has ordered another run of all my SAR wagon kits.)

However, things didn't turn out quite as planned.

Now, anyone who's ever cast in resin without the aid of a vacuum chamber knows that air bubbles are an occupational hazard. Mostly they're either so tiny they can hardly be seen with the naked eye or can be easily attended to with a spot of filler.

On this occasion, though, I had my first experience of the phenomenon of what is known as 'champagne bubbles'.

In fact it was so extreme you could be forgiven for thinking I had used expanding foam instead of polyurethane resin...

What was going on I gather, after a little bit of googling, was the resin was reacting to excess moisture in the air as it cured.

In hindsight I realise I was casting in something of a perfect storm.

The weather had been muggy for days. There were pans of veg boiling away on the stove in the kitchen. And to put the tin lid on it, The Boss was using the steam iron enthusiastically less than a metre away from where I was casting.

(When I say ironing enthusiastically, imagine for a moment a Garratt starting off with all its cylinder cocks wide open - you get the picture)

To test out the theory I rummaged in the loft and brought down the dehumidifier I bought years ago for coping with a condensation crisis in an old house.

I shut the door to the study, left it to run for a while and then mixed up another pot of resin.

I'm pleased to say the resulting casting was flawless and another lesson was learnt.

Namely, don't attempt any casting when the weekly ironing session is in progress.....

1 comment:

  1. Hmm, I wonder if that also explains the odd occasions when using Kristal Klear to glaze a window I end up with lots of bubbles when usually there aren't any at all. I'll have to keep an eye on the humidity next time I try glazing something.