STEP 4 - Disassemble the spacers bars and remove
then replace the desiccant
Now back to the aluminium spacer frame.
On my sealed units the spacer frame is
constructed from straight edges fixed together at the
corners by plastic push-in corner pieces (keys) - this is
fairly standard. These can be pulled-out to allow the
desiccant inside the aluminium spacer bars to be poured out
To remove the corner key hold it right on the
corner and pull directly away from and in-line with the
spacer bar. You may have to make sure all the sealant
cleared from the corner area. Avoid bending the corner key -
it is not strong and you do not want to break it. In
particular do not pull on the free leg of the corner key -
it will simply bend and break.
Keep each spacer bar length horizontal as you
remove its corner key - otherwise the internal desiccant may
just pour all over the floor. Once you have a spacer bar
separated from the rest of the frame take a small container
and tip the desiccant out of the bar.
...carefully pull the corner
inserts out of the hollow spacer bars..
...pour the old desiccant out of
the hollow aluminium spacer bars....
...old desiccant from inside the
sealed unit frame....
If the old desiccant is saturated it may tend
to clump together - so you may have to encourage the
granules out by tapping the bar with a screw driver or
similar. Not too hard however - don't damage the bar.
UPDATE APRIL 2012. IMPORTANT - Don't discard
the saturated desiccant! It can relatively easily be
re-conditioned and re-used in the refurbished unit. This
should give better results than having to use general
purpose silica gel with doubtful dryness..... see below.
Once you have the the spacer bars separated
and emptied of their load of desiccant you can clean them up
a bit more - use the sharp Stanley knife to remove as much
of the remaining sealant from the surface as you can. It
doesn't need to be perfect however.
..remove remaining sealant..
..spacer frame parts - ready for re-use..
The spacer frame parts are now ready to be
re-filled with desiccant and re-assembled.
Absolutely the best desiccant to use to
re-fill the spacer bars is proper
glazing desiccant. This will give the best
performance and longest life for the repaired sealed unit.
Unfortunately I was unable to obtain this (other than by
buying a 25kg box of it!) and I am experimenting with more
generally available silica desiccant (2 to 4 mm bead size).
This isn't ideal and I'll just have to wait and see how long
this lasts, but after about 6 months in-situ my repaired
units have remained clear of condensation. Make sure
whatever type you use keep it in a sealed airtight container
UPDATE APRIL 2012
After about 12 months in situ some of the
refurbished units have started to show re-misting, but only
when the frames are warm from the sun and moisture is driven
out of the general purpose silca gel desiccant I used. Once
the frames cool back down the moisture is reabsorbed and the
The solution to this is to use proper glazing
desiccant as I describe above, OR as I have discovered after
a bit of research, to recondition the saturated glazing
desiccant that you have just removed from the unit. This
turns out to be a relatively straight forward thing to do,
and it involves heating the desiccant granules to drive off
the water molecules held within them. So long as the
temperature is maintained below about 150C the silica gel is
not damaged and it retains its ability to absorb water.
For more information do a Google search for
"reconditioning silica gel desiccant".
The desiccant can be reconditioned by drying
it - heat it up and it will release the moisture it
contains. The heating can be done in an oven slowly, or much
faster in a microwave oven. I have tried only the microwave
method and it appears to work well. I spread the saturated
desiccant I removed from the sealed unit on an shallow
microwave proof dish. In a 850W oven I heated the desiccant
at full for 3 minutes, then removed the dish (taking the
usual hot dish precautions) and stirred the granules a bit
to help the moisture evaporation. BEWARE - THEY WILL BE HOT
TO THE TOUCH. I kept the room well ventilated and carefully
watched for any signs of damage or overheating of the
After the first 3 min heat I could clearly
see the displaced water condensed around the edges of the
dish. I repeated the cycle a further two times, stirring
between heating periods. I then allowed the beads to cool
sufficiently before re-sealing them in an airtight bag ready
for re-insertion in the sealed unit spacer bars.
WARNING do not overheat the beads by using a
more powerful microwave or heating for too long - it may
damage the ability of the silica gel to absorb moisture.
...spread the damp desiccant in a microwave
Heat at 850W for 3 min, repeat a further 2
...click to see more detail. The absorbed
moisture is driven out of the desiccant by the heating...
Once cool enough seal in an airtight bag!
...BEFORE - desiccant newly removed from unit
- humidity meter in the sealed bag shows 50% relative humidity.
The desiccant has lost its ability to dry the air.....
...AFTER RECONDITIONING - the humidity meter
goes off the bottom of the scale. The majority of the water has
been driven off the desiccant and it is ready to resume its
normal drying function in the sealed unit....
You can see the before and after humidity
readings - the simple reconditioning process appears to
successfully remove the water contained in the desiccant
granules leaving them dry and once returned to the spacer
bars, able to do their normal drying job on the air trapped
between the sealed unit's glass panes.
So use the proper glazing desiccant if you can
get it, or recondition the desiccant already in the unit.... it has a smaller grain size
than general purpose silica gel, will last longer and
will avoid potential gap pressure issues by acting only on
water vapour and not other gases in the air gap.
...desiccant I originally experimented with -
glazing desiccant if you can get it... or recondition the
existing desiccant from the frame.
...re-fit the corner keys to one e of the
longer spacer bars...
...carefully pour the new or reconditioned desiccant into the
Re-fit the corner keys to one end of each of
the two longer spacer bars - I found it easier to re-fill
the longer bars first. Then, using a funnel, carefully and
slowly pour the new desiccant into the spacer bar. Stop and
gently tap the bar from time to time to help the desiccant
to settle and fill the bar properly.
...tap the bar from time to time to settle the
...fill to about 1 inch from the top and then
re-fit the corner key...
...carefully pour the new desiccant into the
Fill the bar to about 20mm from the top to
leave enough clear space for the leg of the plastic corner
key to be re-inserted in the bar end. Then re-fit the corner
key. Do the same for both long spacer bars.
Once you have both long spacer bars re-filled
you can re-fit the shorter bars to the corner keys on one of
the long bars. Hold the now partially re-assembled frame
upright and using the funnel again fill each of the upright
shorter spacer bars with new desiccant. Again, tap to help
the desiccant to settle properly and fill the bars, leave
about 20mm or so clear at the top and, once both bars are
filled re-fit the second longer bar with its corner keys to
...fit the shorter bars to one of the filled
longer bars...fill each with new desiccant...
...finally re-fit the remaining filled longer
bar to complete the refurbished spacer frame...
Now you have the spacer frame refurbished
with new desiccant, and two cleaned glass panes you are
ready to reassemble the unit and reseal it.
Next page - for step 5, final cleaning, and
re-assembly of the unit.....