43 replies to this topic

[Arthur Brown]

As you are drying pyro, you really do need to keep the hot wire heaters OUT. They are certain to spark sometime and that once could be disastrous. Please consider http://rswww.com and search
Resistor, Fixed Discrete and Arcol they have some nice ones and they are enclosed elements. The largest ones are water cooled so you could have a closed water circuit piping the heat to your cabinet and a small radiator in there.

[digger]

I have just built a drying cabinet Passfire style, a little smaller though. I have put a home de-humidifier in it (picked up from the local paper adds for £20), no light bulb and no recirculation fan as the de-humidifier puts out quite some draft.

I turned it on at 4pm and at 7.30 the outside temp is 8C and internal temp is 18C I have built all the frames for the screens but I have not put any mesh on them yet, does the following link seem a reasonable price for mesh?

stainless steel mesh

[dr thrust]

hooo nice drying cabinet! turning your own rocket tooling and joinery! the mesh seems pricey, ive used a charcoal impregnated fiberglass mesh fly screen of ebay

[digger]

hooo nice drying cabinet! turning your own rocket tooling and joinery! the mesh seems pricey, ive used a charcoal impregnated fiberglass mesh fly screen of ebay

Thanks, but it is not quite the height of joinery just a few bits of ply, a few screws and a bit of wood glue.

I will have a look around on ebay to see what I can come up with.

The cabinet is up to 37C now so it looks like a temperature controller may be needed.

What is the maximum temperature that a drying cab should be run at?

D

[dr thrust]

i just have a 24 hour timer on mine this "kind of controls" the heat

[GZ22]

Good to see a meaty selection of extinguishers there too!

[digger]

Good to see a meaty selection of extinguishers there too!

Yep you can't be too carefull (at least one of each type), lets hope I never have to use them.

I have now taken delivery of my humidity sensor and the lower measuring limit is 20%. The temperature also seems to have stabilised at 36C and RH below 20%.

So the first question is can you dry stars to quickly?

I had a batch of cut Ruby Red, which have sat not drying for the last couple of weeks. I put them in the cab and they seemed to harden a bit in the first few hours, when I came to them this morning I could press them between my fingers and they would turn to dust. I cannot say whether they are fully dry yet, so I will keep an eye on them to see what happens. Any thoughts on this would be appreciated.

[leosedf]

Which sensor is it?

Depends on the comps you have. Others can be dried fast others need to take it slow.

[Bonny]

So the first question is can you dry stars to quickly?

Stars can be dried too fast. They may crack or with some comps the moisture gets "driven in" and is trapped inside the star while the outside is dry. I believe on passfire, they recommend air drying charcoal streamer type stars under normal conditions for a few days before putting them into the drying box.

[cooperman435]

I recall that dextrin can "case harden" or "dry in" moisture as the dry outer case id very moisture resistant so wont allow the water inside to Wick out through the dry part.

I think in this case having a high humidity but higher temperature may help as the case will still be damp but drier than the inside layers. Otherwise it could just take ages still to dry them totally. My d1 takes ages to dry and untill they are totally dry there weak as hell right up to the last 2 or 3 days when they suddenly go rock hard.

[digger]

I recall that dextrin can "case harden" or "dry in" moisture as the dry outer case id very moisture resistant so wont allow the water inside to Wick out through the dry part.

I think in this case having a high humidity but higher temperature may help as the case will still be damp but drier than the inside layers. Otherwise it could just take ages still to dry them totally. My d1 takes ages to dry and until they are totally dry there weak as hell right up to the last 2 or 3 days when they suddenly go rock hard.

Yep I've heard of drying in, that was one thing I was concerned about. But I was under the impression that this was more of a problem with charcoal based stars such as the D1 that you mention.

I will keep them drying for the next couple of days and see what happens.

Which sensor is it?

Environmental Monitoring Concepts, compact thermo-hygrometer with remote sensor

Edited by digger, 17 January 2008 - 05:43 PM.

[Mumbles]

Shellac has a nasty habit of drying in stars as well. It forms a skin over them.

[Bonny]

Shellac has a nasty habit of drying in stars as well. It forms a skin over them.

I've had that happen with chlorate based stars containing shellac. Although there was a skin overtop in about a day, after a few weeks of drying, insides of stars were still soft. They did light but were still burning when they landed and that's never good.

[paul]

Just to mention it: Shimizu did a great deal of examing which method is suited for cut/rolled/pressed stars and so on. He´s created tables which tell you in detail, which method is suited best.

Maybe it´s woth a look! (for those who have that book)