Kivy ScrollView blur

gistfile1.py

from kivy.uix.label import Label
from kivy.uix.boxlayout import BoxLayout

from kivy.properties import StringProperty

from kivy.base import runTouchApp
from kivy.lang import Builder

Builder.load_string('''
<ScrollableLabel>:
    orientation: 'vertical'
    canvas.before:
        Color:
            rgba: 1, 1, 1, 1
        Rectangle:
            pos: self.pos
            size: self.size
    ScrollView:
        text: str('some really really long string' * 100)
        Label:
            text: str('some really really long string' * 100)
            font_size: '20sp'
            text_size: self.width-10, None
            color: 0, 0, 0, 1
            #   size_hint_y blurs text, try putting # in front:
            size_hint_y: None
            height: int(self.texture_size[1]+10)
            valign: 'top'

    ScrollView:
        size_hint_y: .2
        BoxLayout:
            orientation: 'vertical'
            Button:
                text: 'Bla1'
                font_size: 20
            Button:
                text: 'Bla2'
            Button:
                text: 'Bla3'
''')

class ScrollableLabel(BoxLayout):
    pass

runTouchApp(ScrollableLabel())