Sticky PR

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keithbyrd

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I made my first PR blank and after 30 hours in the pressure pot it was stil sticky and gooey - I put 4 drops of hardner per ounce. What did I do wrong?
 
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I don't know why, but my PR casts seem to take longer to harden in a pressure pot than without pressure. I've taken to leaving my pressure pot (with PR cast inside) in direct sunlight to keep it warm and that seems to help.

Eric
 
It's not uncommon for PR to be sticky or gooy around the top or outer edges of the blank after a day in the pressure tank. It's build that way to allow for multiple pours to adhere to itself. Also, The tank is full of compressed air which is colder, so leaving the blanks I. Longer won't necessarily remove the tackiness. I usually take my blanks out after 20-24 hours and then let sit in direct sunlight or next to the hot air duct for a second day. If it's cold outside, you can keep the blanks inside and near the window or inside the tank with the lid off and a clamp light positioned over it to creat a lightbulb oven. It will cure the tackiness after a couple hours of getting warm and then cooling to room temp for the day.
If the blanks are soft through the middle and squishy I would guess the resin was not mixed enough. Another suggestion, warm your resin to around 80-90 degrees prior to adding the catalyst. It will stir and mix easier. Hotter than that will cause it to cure quickly leaving brittle blanks. I only mix 2-3 drops per ounce to keep the cured resin less brittle. Some have said they put the blanks in an oven to finish curing. I would not recommend that. Not only will you amplify the odor but you will make the resin more brittle and harder to turn without exploding. I hope some of this helps you out. Don't give up. You'll find your routine and it will all work out!
 
What is the temperature where you were casting? If it's 70 you may be in the low 60s in a garage and that's pushing it for PR. I don't like using PR below high 70s but I've cast blanks in the 60s, although I put the pot in direct sunlight like Eric mentioned. I like to pour in the morning with the pot in the sun all day. It's also possible the MEKP may be old. I've never had problems with 6 month old resin, but I've had problems with old catalyst like the blanks not curing or clear blanks having a sort of yellowish or greenish tint. John pretty much nailed everything else, PR really needs to be mixed well, and putting the container in some warm (not hot) water may help.
 
Thanks for all your tips! I definitely am a greenhorn. I din't know about the cool temp sensitivity or the residual stickiness that is normal. I was able to solve my problem with tis blank by heating it in a toaster over - thanks for the tip!
Will be doing another today and will in sure the resin is warmed and the pot is in a warm place!!
 
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