Stupidly simple solution to the form wash evaporation woes


#21

Your solution to the isopropyl alcohol evaporation problem is a good one. Thanks for sharing with us. I thought I would present my solution here in your thread.

I decided to look for a container that the tank would fit into. This army ammunition can from ebay is doing the trick for me.

I had to replace the seal with a new piece of 1/4" rubber so it could hold back the 0.7 psi of vapor pressure.

The ammo can lid is 15" by 12". That vapor pressure would result in a force on the lid of 126 lb. It really adds up for a container this large.

Cheers
Dave


#22

Isnt’ the evaporation happening anyway, just contained?


#23

It happens until an equilibrium is reached between evaporation and condensation. That’s the concept of vapor pressure. If the Form Wash is contained, then there will be much less evaporation, as the vapor can’t escape and an equilibrium is reached quickly. On the other hand, with an uncontained, unsealed Form Wash, the vapor can escape and there will never be such an equilibrium, the IPA will just continue evaporating until it is gone.


#24

Do you end up with a film of condensation coating the outside of your Form Wash?

Nice case BTW; guess the ammo box is also handy if your Wash spontaneously explodes.


#25

Only the tank from the Form Wash is in the ammo can. I have not noticed any condensation on it yet. If there is some after a longer period of time I will report back.


#26

Opened the ammo can first time today after printing a part. It has been 18 days. You will probably not be surprised to hear that there was zero measurable alcohol loss.

Cheers
Dave


#27

Yes, there is condensation on the inside of the ammo can. But it is very little, no visible droplets just looks and feels damp to the touch. It has softened the paint in the inside of the can. Odd but there is no condensation on the outside of the form wash tank at all !? I have no idea why. If you do not open the can for a week, you will hear vapor pressure escaping (pfsssst) as you open the lid clamp on one side like opening a beer. Then you get hit with the fumes as you reach in to get the tank but it only lasts for a second and it is gone. The total loss of IPA from the ammo can that I can measure has been zero. Without it I would have lost litres of IPA from this thing and would have been breathing it every day.


#28

With great help and advice from Nick at Form Labs I switched to using TPM instead of IPA. It’s been such a positive move in every way. I no longer fear the fire risk, it doesn’t smell or give headaches, and best of all it does a much much better job of removing trapped resin from small crevices. We used to do a course wash with dirtier IPA and a fine wash with clean IPA but now it’s a 20 min wash in TPM followed by just a rise in water. The TPM is food safe, non-flammable, and lasts much longer than IPA (holds more resin). Problems I used to have that I thought were just the resin being poor (Black in particular) have gone away, turns out it was trapped resin that IPA wasn’t washing away. The TPM is hard to buy in small quantities, but hopefully that will change. It doesn’t evaporate at all, in fact we have growing level as it becomes more resin-full! No looking back.


#29

Where did you purchase the TPM?


#30

Will the alcohol fumes melt through your Saran Wrap? I’ve been thinking that your idea seems to be the most convenient!


#31

Hasn’t melted through yet. The saran wrap does get icky after a while, I just replace it. While not very sophisticated, the simple saran wrap trick does seem to help - my partner complains less about alcohol smells emanating from it. Keeping a weight on top (like a partially full cartridge) helps keep things tight.