Well, I had an interesting experience today.

Yesterday, I was talking with a musician who told me about the first guitar he had made for himself by a luthier. The musician was impatient to get the guitar, but the luthier told him he must only work at certain temperatures for the best results, so the musician must be patient.

It made me think about how much my epoxy and varnishing work is governed in the same way by temperature.

This morning I glassed the interior of a small canoe.

If you've looked at my "Shop Tips" pages you will know I normally heat my shop up to 80 - 85˚ in the afternoon and let the temperature start to drop, to avoid bubbles in the resin/glass lay-up from the wood cells "off gassing" the expanding air.

Once these micro bubbles are formed they get burst by sanding or wear and leave holes so small surface tension will never allow them to be filled. These pathways do allow water vapor absorption into the wood core which will cause later problems so they should be avoided at all costs.

Of course, sometimes it is a PITA to have to heat the whole shop up and then let it start to cool before glassing.

So, this morning I wanted to glass the interior of this canoe hull I had sanded the previous day.

I was impatient.

My shop was at 72˚ and I could see as I worked, the temperature started to rise, so I opened my shop doors to cool the shop down and prevent off gassing of the lay-up. And it worked, the outdoor temperature was in the mid 60˚s and the shop temperature slowly dropped and I saw no evidence of bubbles.

On my hull interiors I do a one step wet-out of the glass and wood. As you may know, I normally do a seal coat on exterior wood to ensure a transparent lay-up, see my web page for details @ http://www.laughingloon.com/epoxy.html

I have not done a glass/wood wet-out at lower shop temperatures for a LONG time. Now I remember why!

With the shop around 70˚ I knew the resin would be much thicker in consistency than when I normally use it at 85˚. But I still wanted to give the resin as much time as possible to saturate the glass and wood, so I used MAS epoxy with a slow hardener. I now use MAS for interior wet-outs where transparency is not as critical. MAS sets-up much faster than the System Three epoxy I use for exterior wet-outs. I use the slower setting System Three resin because it wets glass fibers more thoroughly and cures to a smoother surface. Even at 85˚ the System Three resin with slow hardener takes about 12 hours to become tack free.

BUT!!! What a difference the temperature makes! At 70˚ the MAS resin was so much thicker than I was accustomed to working with. This caused more resin to be applied because it was just thicker on the roller cover, on the glass and everywhere. The thick resin sat on top of the glass without penetrating into the wood, causing it to stick to the roller, pulling the glass off the hull sides. At higher temperatures with the resin much thinner the resin penetrates through to the wood very quickly so the roller doesn't lift the glass.

When I tried to remove the excess resin with a squeegee, I could feel how thick the resin was and how the excess resin refused to move through the glass. Even so, I removed 9 oz., a full cup of resin, because the resin had gone on so thick from the start. At 68˚ the MAS epoxy with slow hardener cured to tack free in 4 hours! That was a surprise. No wonder MAS cures to an orange peal surface with those little molecules moving so fast!

So while anyone else would have felt its was a great success, I could see the cooler working temperature caused a much heavier than normal lay-up for me.

Now I have refreshed my memory on just why I do wet-outs with higher temperatures. At higher temperatures the resin is much thinner, wetting out glass and wood quickly. By using small batches the resin remains as thin as possible allowing me to remove a great deal of excess resin with the squeegee. When you are used to working alone you have a limited perspective.

This reminded me of one of my classes, where I demonstrated glass/wood wet-out, and a student who had built a stripper before commented that he was surprised at how little resin I used and how little I removed.

Thinking about Nick's recent "infusion" experiment and times when I've had other builder's tell me about vacuum bagging, giving a super lightweight lay-up, makes me wonder just how close my lay-up technique is to the weights achieved with those complex glassing methods.

Everything boils down to the attention to details. Temperature is a very important detail in glassing a stripper.

I hope this will be of help to some of you!

All the best,
Rob

AKA - "the perfectionist" by Mr. Babina