Casting in winter... arrrggghhh!

[Anvils Hammer]

Just sharing pain here really..

Resins cure best between 18-25 degrees Celcius

Its current about 6 degrees outside and I have to cast in a shed.. My heater in there is going full blast but its still only around 12 degrees in there.

Im putting the resin cans right next to the heater to keep the resin warm, but the parts are still coming out really brittle.

I find (hope) that if I leave them a few days they harden up to have the same final properties as a part cast at 22 degrees, but its still really annoying!!

Back in summer I had the opposite problem, shed like an oven.. was casting at 30 degrees and getting serious air bubbles due to drastically shortened pot life!

How do you guys deal with tempreature fluctuations? Im looking forward to getting a dedicated tempreature controlled casting room, but that is a while off realisistically..

AH

[Lane]

Store the resin and RTV indoors where the temp is constant.
Take the materials out to the shed in an insulated box or a 'cooler' (not sure what UK term for portable ice chest is) to reduce heat loss. Only remove long enough to measure.
Warm your molds before pouring.

Doing this should let you cast for an hour or so at those temps.

You may want to build a temp controlled cabinet for your casting supplies. A couple high wattage light bulbs or better Halogen bulbs will keep an insulated cabinet fairly warm. If using halogen lights a metal cabinet and non flammable insulation would be best, those bulbs get hot. By adding an air duct you could hook it up to an AC unit in the summer. With short cure times of most resin the initial temp, and mold temp, are probably a lot more important than air temp.

[mangozac]

[blind pig]

Ha, I used to get these problems when I lived in Canberra. -6 degrees in winter and near 40 degrees in summer. I just used to put up with it and cast something else.

As lane said, get a cupboard to store the resins in your shed and have a incandescent light bulb in there to warm it up. I wouldn't go past 40-60W, as they do put out a fair amount of heat. A light bulb will also help to heat up the shed.

You may also have to post pour cure your brittle PU by putting the mould & job in a hot box. An esky or polystyrene foam box with an "in" and "out" hole and a small blower heater or hair dryer would work pretty well to heat resin and mould to get all that PU to cross link and cure fully.

Perhaps try an old toaster oven and an additional thermometer to check the temps and try and hit above 80 degrees to 100 degrees celsius.

[Lane]

I had to get a small refrigerator to keep casting supplies in. I do my casting in the garage which get good airflow from the house so it is always warmer in summer/ cooler in winter. To keep the garage at a comfortable (for the materials, I can deal with heat/ cold) would cost an extra $75 per month and mean the house was 10-15 F warmer/ cooler than normal. Since I'm single and tend to work long days I also let the house get warmer comfortable (in the summer) while I'm at work. That saves me another $75-100 per month but would be really bad for the resin. Now I just need to get a thermostat and a light to heat the refrigerator for the next few months.

[Anvils Hammer]

Cheers for the advice! glad its not just me with this issue..

Ive got a hot air gun that kicks out 450 degree Celcius air.. I can warm a box up pretty damn quick!

Keeping the materials in the house is a good idea, so long as I put the lids on nice and tigh, saves me having to warm them.

The parts cure up ok in the molds, takes about 30 minutes, I think post curing them at a higher temp would be a good idea, a tray of parts in a lamp box would work I think..

AH